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  • Inorganic Chemistry
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  • 1997  (75)
  • 1
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    Communications in Numerical Methods in Engineering 13 (1997), S. 47-49 
    ISSN: 1069-8299
    Keywords: nonlinear structural analysis ; arc-length algorithm ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this paper, we have proved in theory that the sign of the current stiffness matrix provides a correct indicator for determining the sign of the loading parameter in the arc-length algorithm before the first bifurcation point is encountered, but may not be the case thereafter. © 1997 John Wiley & Sons, Ltd.
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  • 2
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 887-903 
    ISSN: 0029-5981
    Keywords: multigrid ; adaptive agglomeration ; additive correction ; anisotropic grids ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the computational simulation of fluid flow and scalar transport, multigrid iterative solution techniques often fail or stall when the discrete linearized equations have strongly anisotropic coefficients. In the present work, an adaptive agglomeration algorithm for forming coarse grids is presented that allows multigrid techniques to work efficiently for equation sets with anisotropic coefficients. The adaptive agglomeration is defined by two rules and several guidelines that follow from a physical interpretation of the performance of iterative solvers like Gauss-Seidel. The effectiveness of the adaptive agglomeration algorithm is demonstrated for a wide range of test cases. © 1997 by John Wiley & Sons, Ltd.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 21 (1997), S. 825-843 
    ISSN: 0363-9061
    Keywords: fracture modelling ; granular materials ; numerical modelling ; Engineering ; Civil and Mechanical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: This paper describes the computer algorithms used in a numerical simulation of the compression of an aggregate of crushable grains. It has been used in a model for the evolution of a granular medium under one-dimensional compression, in which the probability of fracture for individual particles is a function of applied stress, particle-size and co-ordination number. The information relating to the particles is represented in a compact way on the computer which allows the number of particles produced to become sufficiently large for satisfactory comparisons to be made with experimental data and which allows information, such as the positions and sizes of the particles, to be easily extracted. An algorithm based on the representation is used to locate neighbouring particles in a way which does not deteriorate unacceptably in terms of speed as the number of particles increases. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 13 Ill.
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  • 4
    ISSN: 0044-2313
    Keywords: Arylxenon trifluoromethanesulfonates ; electrophilic aromatic substitution ; xenontrifluoroacetate trifluoromethanesulfonate ; NMR spectra ; X-ray crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Die direkte Synthese von Arylxenontrifluormethansulfonaten durch elektrophile SubstitutionBei der Reaktion von Xenonbis(trifluoracetat) mit Trifluormethansulfonsäure wird die neue, hochreaktive, unsymmetrische Xenon-Sauerstoff-Verbindung CF3COOXeOSO2CF3 erzeugt. Benzolderivate mit elektronenziehenden Substituenten wie F, CF3, Cl und NO2 werden von diesem Intermediat unter Bildung von Arylxenontrifluormethansulfonaten elektrophil angegriffen. Über diese Eintopfsynthese wurden Trifluormethansulfonate mit den Kationen [Xe(2,4,6-F3C6H2)]+, [Xe(2-F-5-NO2C6H3)]+, [Xe(2-F-5-CF3C6H3)]+ und [Xe(3,5-(CF3)2C6H3)]+ synthetisiert. Alle Verbindungen wurden durch ihre NMR-, Massen- und Schwingungsspektren charakterisiert.Zusätzlich wurden mehrere neue Arylxenontrifluormethansulfonate als Produkte der Umsetzungen von 1,3-F2C6H4 und weiteren desaktivierten Benzolen mit Xenon(trifluoracetat)trifluormethansulfonat anhand der 129Xe-NMR-Spektren identifiziert.Fluorsubstituenten in ortho-Position zu Xenon erhöhen signifikant die thermische Stabilität der Arylxenontrifluormethansulfonate.Die Molekülstruktur von [Xe(2,6-F2C6H3)][OSO2CF3] wurde durch eine Einkristallröntgenstrukturanalyse bestimmt. Die Arylxenoneinheit koordiniert schwach mit einem Sauerstoffatom des CF3SO3-Anions. Die Verbindung kristallisiert in der triklinen Raumgruppe mit a = 880.9(3) pm, b = 1093.9(5) pm, c = 1209.8(5) pm, α = 89.04(4)°, β = 74.23(3)°, γ = 86.03(3)°, Z = 4.
    Notes: The reaction of xenonbis(trifluoroacetate) and trifluoromethanesulfonic acid (triflic acid) gave the new, highly reactive unsymmetrical xenon-oxo species CF3COOXeOSO2CF3. Benzene derivates, containing electron withdrawing substituents such as -F, -CF3, -Cl or -NO2 were electrophilic attacked by this intermediate to yield arylxenon trifluoromethanesulfonates. Via this one-pot synthesis trifluoromethanesulfonates with the cations [Xe(2,4,6-F3C6H2)]+, [Xe(2-F-5-NO2C6H3)]+, [Xe(2-F-5-CF3C6H3)]+ and [Xe(3,5-(CF3)2C6H3)]+ were prepared. All compounds were characterized by their NMR, mass, and vibrational spectra.Additionally, several new arylxenon trifluoromethanesulfonates were detected by 129Xe-NMR spectroscopy as products of the reaction of 1,3-F2C6H4 and further deactivated benzenes with xenontrifluoroacetate trifluoromethane sulfonate.Fluoro substituents in ortho position to xenon significantly increase the thermal stability of the arylxenon trifluoromethanesulfonates obtained.The molecular structure of [Xe(2,6-F2C6H3)][OSO2CF3] was determined by single crystal diffraction methods. The arylxenon unit is weakly coordinated by one oxygen atom of the CF3SO3 anion. The salt crystallizes in the triclinic space group P1, a = 880.9(3) pm, b = 1093.9(5) pm, c = 1209.8(5) pm, α = 89.04(4)°, β = 74.23(3)°, γ = 86.03(3)°, Z = 4.
    Additional Material: 7 Ill.
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  • 5
    ISSN: 0009-2940
    Keywords: Mercury ; Lanthanides ; Lanthanoid(II) complexes ; (N-2,6-Diisopropylphenyl)(N-trimethylsily)amide complexes ; Bis(trimethylsilyl)amide complexes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Mercury(II) amide complex Hg[N(SiMe3)(2,6-iPr2C6H3)]2 (1) was prepared by reaction of HgBr2 with Li[N(SiMe3) 2,6-iPr2C6H3)] in diethyl ether solvent. Redox transmetallation reactions of 1 with elemental samarium, europium or ytterbium in THF solvent (THF = tetrahydrofuran), generated the novel divalent complexes Ln[N(SiMe3)(2,6-iPr2C6H3]2(THF)2 with Ln = Sm (2), Eu (3) and Yb (4). 4 was also synthesized by reaction of elemental ytterbium, HgPh2 and HN(SiMe3)(2,6-Me3)2]2(THF)2 [Ln = Sm (5), Yb (6)] by reaction of the metals with HgPh2 and HN(SiMe3)2. Thermal desolvation of 4 under high vacuum gave Yb(N)(SiMe3)2,6-iPr2C6H3)]2 (THF) (7), whereas under identical conditions 6 yielded the solvent-free complex [Yb[N{SiMe3)2]2]2. (8). The new compounds 1-4 and 7 are hydrocarbon soluble and 171Yb-NMR spectra were recorded for 4, 6, 7 and 8. X-ray crystal structure determinations of 2 and 4 revealed four-coordinate, distorted tetrahedral metal environments augmented by weak Ln…ipso-C(aryl) interactions.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 1147-1150 
    ISSN: 0009-2940
    Keywords: Icosahedral heteroboranes ; Ab initio calculation ; Bonding models ; Aromaticity ; Nucleus Independent Chemical Shift [NICS] ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio theoretical studies on X2B10H10 (X = CH, SiH, N, P and Sb) have been done for all the three possible isomers. Unlike lower-vertex heteroboranes, all the hetero derivatives have shown similar trends in the relative stabilities, the 1,12-isomer being more stable followed by 1,7- and 1,2-isomers, except for N and Sb. No conventional 1,2-isomer for N could be found. Instead, a new nido isomer which is 18.1 kcal/mol higher in energy than the most stable isomer has been located. Any hetero group substitution to icosahedral R12H122- is found to be thermodynamically destabilizing. However, the Nucleus Independent Chemical Shift criterion shows that all compounds, except for 8, have similar aromaticity.
    Additional Material: 2 Tab.
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  • 7
    ISSN: 0009-2940
    Keywords: Platinum ; Ruthenium ; Cluster anions ; Phosphanes ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reactions of [Pt3Ru6(CO)21(μ-H)3(μ3-H)] (1) with PMe3 and PPh3 have produced the salts [Pt(PR3)3H]-[Pt3Ru6(CO)21(μ3-H)(μ-H)2], 5a and 5d, R = Me and Ph in the yields 9% and 22%, respectively. By contrast the reaction of 1 with PPh3 in the presence of Me3NO has yielded the phosphane-substituted derivative [Pt3Ru6(CO)20(PPh3)μ-H)3(μ3-H)] }(6) in 22% yield. Compounds 5a and 6 were characterized by single crystal X-ray diffraction analysis. Compounds 5a and 5d are salts of the anion [Pt3Ru6(CO)21(μ3-H)(μ-H)2]-. The anion contains a layer segregated Ru3Pt3Ru3 structure similar to that of 1 with two bridging hydride ligands on one Ru3 triangle and one semi-triply bridging hydride ligand on the other. The cation [Pt(PR3)3H]+ was evidently formed by the abstraction of platinum from other molecules of 1. Compound 6 is a PPh3 derivative of the parent 1 that also contains the layer segregated stacking of Ru3 and Pt3 triangles. The PPh3 ligand is coordinated to one of the ruthenium atoms in an axial position.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 130 (1997), S. 63-67 
    ISSN: 0009-2940
    Keywords: Barium ; Copper ; Arsenate ; Magnetic susceptibility ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two new compounds Cu4(AsO4)2O (1) and Ba2Cu7As6O24 (2) were obtained from a mixture of CuO and As2O5 · xH2O heated to 1090°C for 72 h in a BaCO3 flux. Compound 1 was obtained as dark green crystals, belonging to the orthorhombic crystal system. Compound 2 was obtained as light gray to colorless crystals belonging to the triclinic crystal system. The structure of 1 contains two copper ions with distorted trigonal bipyramidal geometries and a third with a distorted square pyramidal geometry. One ‚oxide‘ ion is surrounded by four copper ions in a distorted tetrahedral arrangement. Compounds 2 consists of two chains with alternating units of trigonal bipyramidal CuO5 and square planar CuO4 units, with the oxygen atoms derived from the AsO4 groups. Magnetic susceptibility measurements of 1 and 2 both show effective magnetic moments, μeff=1.90-1.95 B.M./Cu at 25°C, which is consistent with Cu2+ ions having one unpaired electron. Significant antiferromagnetic coupling was revealed by variable temperature measurements. At very low temperatures (15-25 K) samples of both 1 and 2 undergo a transition to a weak ferromagnetic state.
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  • 9
    Electronic Resource
    Electronic Resource
    Chichester, West Sussex : Wiley-Blackwell
    Mathematical Methods in the Applied Sciences 20 (1997), S. 1313-1323 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: We investigate an initial-value problem modelling fragmentation processes where particles split into two or more pieces at a rate, γ, that not only depends on the sizes of the particles involved but also on time. The existence of non-negative, mass-conserving solutions is established by considering a truncated version of an associated non-autonomous abstract Cauchy problem. The latter has solutions of the form u(t)=Un(t,t0)f, t≥t0, where f is the known data at some fixed time t0≥0 and {Un(t,s)}t0≤s≤t≤T is a uniformly continuous evolution system. A limit evolution system {U(t,s)}t0≤s≤t≤T is shown to exist. Depending on the form of the known data f at time t0, the scalar-valued function u, obtained from the limit evolution system via u(x, t)=[U(t, t0)f](x) for a.e. x〉0, t≥t0, is a solution of either the original initial-value problem or an integral version of this problem. © 1997 B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester, West Sussex : Wiley-Blackwell
    Mathematical Methods in the Applied Sciences 20 (1997), S. 1379-1388 
    ISSN: 0170-4214
    Keywords: Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics
    Notes: The theory of high-frequency waves has been used to calculate first and second-order asymptotic solutions for the propagation of non-linear waves in a cylindrical symmetric flow of an electron plasma. The behaviour of acceleration waves and weak shock waves has been analysed through these solutions and Whitham's rule for a weak shock wave on any wavelet has been confirmed through the first-order solution. The appearance of a weak shock wave on any wavelet has been determined and its strength, the location, and the speed of propagation have been found from the asymptotic solution presented in this paper. © 1997 by B. G. Teubner Stuttgart-John Wiley & Sons Ltd.
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