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  • Articles  (99)
  • cluster analysis
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  • Geosciences  (86)
  • Mathematics  (62)
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  • Articles  (99)
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  • 1
    Electronic Resource
    Electronic Resource
    Experiences with applying a genetic algorithm to determine an information systems architecture (1997)
    Springer
    OR spectrum 19 (1997), S. 47-53 
    Details
    ISSN: 1436-6304
    Keywords: Information systems architecture ; business Systems planning ; cluster analysis ; genetic algorithms ; Architektur von Informationssystemen ; Business Systems Planning ; Cluster-Analyse ; Genetische Algorithmen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Description / Table of Contents: Zusammenfassung Zur Entwicklung von Architekturen von Informationssystemen (ISA) wird vielfach das Business-Systems-Planning-(BSP)-Konzept vorgeschlagen. Ein Teilproblem dieses Planungskonzepts besteht darin, unter Berücksichtigung von Optimalitätskriterien Unternehmensprozesse und Datenbestände zu möglichst voneinander unabhängigen Teilsystemen zusammenzufassen. Da die Leistungsgrenzen von exakten Optimierungsverfahren für dieses Problem rasch erreicht werden, interessiert der Einsatz von heuristischen Verfahren. Zunächst werden das BSP-Problem und die Vorgehensweise genetischer Algorithmen kurz erläutert. Danach wird die Anwendung eines einfachen genetischen Algorithmus auf das BSP-Problem beschrieben. Ein Vergleich mit Ergebnissen exakter Verfahren bildet einen weiteren wichtigen Bestandteil der Untersuchung.
    Notes: Abstract While determining information systems architectures (ISA), business systems planning (BSP) is a well-known method to join processes and data classes to subsystems. BSP matrices have generally been rearranged without describing the underlying methods. Meanwhile, various techniques have been developed for solving the ISA problem. Since exact optimization methods often fail to provide results for large ISA problems, different heuristics have been applied. A new heuristic for solving the ISA problem is the application of genetic algorithms (GA). This paper examines the application of a simple GA to the ISA problem and compares the results of applying the GA with those obtained by exact methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01539808
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  • 2
    Electronic Resource
    Electronic Resource
    Experiences with applying a genetic algorithm to determine an information systems architecture (1997)
    Springer
    OR spectrum 19 (1997), S. 47-53 
    Details
    ISSN: 1436-6304
    Keywords: Key words: Information systems architecture ; business systems planning ; cluster analysis ; genetic algorithms ; Schlüsselwörter: Architektur von Informationssystemen ; Business Systems Planning ; Cluster-Analyse ; Genetische Algorithmen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Description / Table of Contents: Zusammenfassung. Zur Entwicklung von Architekturen von Informationssystemen (ISA) wird vielfach das Business-Systems-Planning-(BSP)-Konzept vorgeschlagen. Ein Teilproblem dieses Planungskonzepts besteht darin, unter Berücksichtigung von Optimalitätskriterien Unternehmensprozesse und Datenbestände zu möglichst voneinander unabhängigen Teilsystemen zusammenzufassen. Da die Leistungsgrenzen von exakten Optimierungsverfahren für dieses Problem rasch erreicht werden, interessiert der Einsatz von heuristischen Verfahren. Zunächst werden das BSP-Problem und die Vorgehensweise genetischer Algorithmen kurz erläutert. Danach wird die Anwendung eines einfachen genetischen Algorithmus auf das BSP-Problem beschrieben. Ein Vergleich mit Ergebnissen exakter Verfahren bildet einen weiteren wichtigen Bestandteil der Untersuchung.
    Notes: Abstract. While determining information systems architectures (ISA), business systems planning (BSP) is a well-known method to join processes and data classes to subsystems. BSP matrices have generally been rearranged without describing the underlying methods. Meanwhile, various techniques have been developed for solving the ISA problem. Since exact optimization methods often fail to provide results for large ISA problems, different heuristics have been applied. A new heuristic for solving the ISA problem is the application of genetic algorithms (GA). This paper examines the application of a simple GA to the ISA problem and compares the results of applying the GA with those obtained by exact methods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01539808
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  • 3
    Electronic Resource
    Electronic Resource
    X-ray structure of 5-phenyl-1,3,4-oxathiazol-2-one (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 25-28 
    Details
    ISSN: 1572-8854
    Keywords: Oxathiazolone ; structure ; nitrile sulfide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystal structure of 5-phenyl-1,3,4-oxathiazol-2-one has been determined. Colorless, regular plate shaped crystals of C8H5O2NS crystallize in the monoclinic space group P21/n (#14) with cell dimensionsa=11·161(8),b=7·1470(20),c=19·864(15) Å and β=99·77(4)°;V=1561·5(17) Å3 andZ=8.1725 unique reflections withl net〉2.5σ(l) on refinement afforded values ofR=0.054 andR w=0.049.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666190
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray structure of tricyclohexylmethyl chloride (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 539-542 
    Details
    ISSN: 1572-8854
    Keywords: Tricyclohexylmethyl chloride ; structure ; tricylohexylmethyl
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The X-ray crystallographic structure of tricyclohexylmethyl chloride, a precursor of the tricyclohexylmethyl radical, has been determined. Colourless tablets of C19H33Cl crystallized from hexane/chloroform in the orthorhombic space group Pnma, with cell dimensions a=10.725(3),b=15.670(3),c=10.168(3) Å;V=1708.8(1.3) Å3;Z=4. 1586 reflections withI〉3 σ(I), and 302 with zero intensity, on refinement gaveR=0.046,R w=0.076. The three cyclohexyl rings are arranged to give the molecule a plane of symmetry containing the central C−H axis. The large volume per nonhydrogen atom, of about 21.3 Å3, is close to values found in the crystal structures of analogous tricyclohexyl compounds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01668412
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  • 5
    Electronic Resource
    Electronic Resource
    The formation of a Schiff base intermediate: a nickel(II) complex of an asymmetric tripodal ligand (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 207-210 
    Details
    ISSN: 1572-8854
    Keywords: Tripodal ligand ; Ni(II) complex ; quinoline ; carbinoxyamine ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Treatment of Ni(ClO4)2 · 6H2O with the condensing product of 2-formylpyridine N-oxide and 1,5-diamino-3-(8-methylquinolyl)azapentane (dmqa) has resulted in the formation of an asymmetric tripodal nickel(II) complex, [C28H32N6O3Ni](ClO4)2 · H2O, which has been crystallographically characterized. Crystal data: triclinic, space group p ī, a = 10.384(2), b = 10.911(3), c = 16.6101(11) Å, α = 95.62(2), β = 105.04(2), γ = 112.954(11)°, D c = 1.581 g/cm3, Z = 2 and V = 1631.0(6) Å3. A quinoline moiety is first introduced into an arm in the complex of a tripodal ligand in which an ethylcarbinoxyamine group, the intermediate of Schiff bases, exists.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009578329008
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  • 6
    Electronic Resource
    Electronic Resource
    Crystal structure and conformational analysis of N-formyl and N-nitroso derivatives of piperidinone (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 769-775 
    Details
    ISSN: 1572-8854
    Keywords: structure ; conformation ; equatorial ; axial orientations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Single crystal X-ray studies for N-formyl-2,6-diortho chlorophenyl-3,5-dimethyl piperidin-4-one (FOCDMPO) and N-nitroso-2,6-di(3′,4′,5′-trimethoxyphenyl)-3,5-dimethyl piperidin-4-one (NTMPO) are reported. Crystals of FOCDMPO and NTMPO belong to the monoclinic space groups P21/n and C2/c, respectively. FOCDMPO: a = 9.147(2), b = 14.586(3), c = 13.665(5) Å and β = 101.68(2)° NTMPO: a = 38.52(2), b = 13.727(5), c = 9.564(3) Å and β = 98.60(1)°. In both the structures, the piperidine ring adopts a boat conformation with slight distortion. In FOCDMPO, one of the phenyl and methyl groups are in axial positions while the other phenyl and methyl groups are in equatorial orientations. In NTMPO, the situation is reversed. The molecules are stabilized by weak intermolecular C—H ··· O interactions in addition to van der Waals forces.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009587518299
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  • 7
    Electronic Resource
    Electronic Resource
    Crystal structure refinement of nitroguanidine (1999)
    Springer
    Journal of chemical crystallography 29 (1999), S. 671-676 
    Details
    ISSN: 1572-8854
    Keywords: nitroguanidine ; energetic molecule ; structure ; oxidizer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of nitroguanidine was refined using X-ray single-crystal diffraction methods. Previous structure determinations achieved with single crystal photographic or neutron powder techniques yielded values for the C—N ‘formal’ double bond-length that either equaled or exceeded the ‘formal’ C—N single-bond lengths. Bond lengths were more precisely and accurately determined here than in the previous studies, but the ‘formal’ double-bond length still exceeds the ‘formal’ single bond lengths. Comparisons of crystal bond lengths with ab initio derived bond lengths of an isolated nitroguanidine molecule and hydrogen-bonded clusters of nitroguanidine molecules suggest that observed bond-length abnormalities are caused by intermolecular forces in the crystal. The crystal is orthorhombic, with a = 17.6390(5), b = 24.8730(7), c = 3.5903(1) Å, V = 1575.19 Å3, Z = 16, and D calc = 1.736 g cm−3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009519703355
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  • 8
    Electronic Resource
    Electronic Resource
    The structure of dimethylcrocetin (1994)
    Springer
    Journal of chemical crystallography 24 (1994), S. 739-742 
    Details
    ISSN: 1572-8854
    Keywords: Dimethylcrocetin (DMCRT) ; carotenoids ; structure ; saffron ; Crocus sativus L
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The structure of dimethylcrocetin (DMCRT), prepared by alkaline hydrolysis in methanol of the glucosidic carotenoids extracted from the stigmata of theCrocus sativus L. flowers, has been determined. The molecule has the all-trans configuration and is planar forming a long conjugated system. The C−O bond length values of the two ester groups are shortened as expected. The compound (C11H14O2)2 crystallizes in the orthorhombic space group Pbcn witha=12.5907(7),b=7.5639(5) andc=21.963(2)Å. Dimethylcrocetin has characteristic Infrared absorptions at 1697 cm−1 ϑ (C=O) and 1229 cm−1 ϑ (C−O) and characteristic Raman vibrational modes at 1542 cm−1 ϑ (C=C) and 1166 cm−1 ϑ (C−C).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01666962
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  • 9
    Electronic Resource
    Electronic Resource
    X-ray crystal structure and1H-NMR chiral shift reagent study of a crown trimer (1995)
    Springer
    Journal of chemical crystallography 25 (1995), S. 759-762 
    Details
    ISSN: 1572-8854
    Keywords: Cyclooligomerization ; orthocyclophanes ; structure ; X-ray diffraction ; C−H...O molecular interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract 3,4,5-Trimethoxybenzyl alcohol was cyclooligomerized with a bentonite clay used as a catalyst. Results of the crystal structure analysis of the racemic (±) nonamethoxy[1,1,1]orthocyclophane trimer, C30H36O9, are described. The structure was determined by X-ray diffraction at 293 K and shown to belong to the triclinic space group P $$\bar 1$$ . The compound possesses a distorted crown conformation with unusual C−H...O intermolecular interactions, and with a crystal packing not observed before in other related derivatives. The racemic mixture was also discriminated in its two enantiomeric isomers, using proton NMR and Eu(III) as a chiral shift reagent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01670332
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  • 10
    Electronic Resource
    Electronic Resource
    Structure of the [5S,15S] isomer of the macrocyclic complex, [La(NCS)3(C24H30N6)] (1996)
    Springer
    Journal of chemical crystallography 26 (1996), S. 9-13 
    Details
    ISSN: 1572-8854
    Keywords: Lanthanum ; hexaazamacrocyclic complex ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal and molecular structure of the [5S,15S] isomer of the [LaL(NCS)3] complex (L=C26H30N6) was determined by single crystal X-ray diffraction analysis. The compound crystallizes in the orthorhombic space group P212121 witha=13.647(4),b=19.504(4),c=11.606(4)Å. The 9-coordinate La(III) is bound to the N atoms of three monodentate isothiocyanates and to the six N atoms of the macrocycle ligand L, which has an 18-membered, six-nitrogen donor cavity and two peripheral −CH3 substituents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02018690
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