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  • 1985-1989  (675)
  • 1945-1949
  • 1989  (675)
  • Engineering General  (536)
  • Genetics  (139)
  • 101
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 741-745 
    ISSN: 0271-2091
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 102
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 747-761 
    ISSN: 0271-2091
    Keywords: Navier-Stokes solutions ; Shock wave/boundary layer interactions ; Newton's iteration ; Upwind differencings ; Symmetric line relaxation ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The objective of the paper is twofold. First we describe an upwind/central differencing method for solving the steady Navier-Stokes equations. The symmetric line relaxation method is used to solve the resulting algebraic system to achieve high computational efficiency. The grid spacings used in the calculations are determined from the triple-deck theory, in terms of Mach and Reynolds numbers and other flow parameters. Thus the accuracy of the numerical solutions is improved by comparing them with experimental, analytical and other computational results. Secondly we proceed to study numerically the shock wave/boundary layer interactions in detail, with special attention given to the flow separation. The concept of free interaction is confirmed. Although the separated region varies with Mach and Reynolds numbers, we find that the transverse velocity component behind the incident shock, which has not been identified heretofore, is also an important parameter. A small change of this quantity is sufficient to eliminate the flow separation entirely.
    Additional Material: 12 Ill.
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  • 103
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 865-869 
    ISSN: 0271-2091
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 104
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 891-920 
    ISSN: 0271-2091
    Keywords: Transient flows ; Oscillating aerofoil ; Dynamic stall ; Navier-Stokes equations ; Finite differences ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Unsteady viscous flow around a large-amplitude and high-frequency oscillating aerofoil is examined in this paper by numerical simulation and experimental visualization. The numerical method is based on the combination of a fourth-order Hermitian finite difference scheme for the stream function equation and a classical second-order scheme to solve the vorticity transport equation. Experiments are carried out by a traditional visualization method using solid tracers suspended in water. The comparison between numerical and experimental results is found to be satisfactory. Time evolutions of the flow structure are presented for Reynolds numbers of 3 × 103 and 104. The influence of the amplitude and frequency of the oscillating motion on the dynamic stall is analysed.
    Additional Material: 10 Ill.
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  • 105
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1302-1304 
    ISSN: 0271-2091
    Keywords: Incompressible flow ; Clebsch potentials ; Three-dimensional ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A recent paper by W. Zijl, which reformulated the Navier-Stokes and Boussinesq equations in terms of Clebsch potentials, has an error that greatly reduces the generality of the results. Some other recent efforts to use such potentials in fluid and plasma dynamics are briefly discussed.
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  • 106
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1299-1301 
    ISSN: 0271-2091
    Keywords: Navier-Stokes equation ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: In a recent paper a generalized potential flow theory and its application to the solution of the Navier-Stokes equation are developed.1 The purpose of this comment is to show that the analysis presented in that paper is in general not correct. We note that the theoretical development of Reference 1 is in fact an extension - although not cited - of some work first done by Hawthorne for steady inviscid flow.2 Hawthorne's solution is correct, and his analysis, which we briefly describe, provides a useful introduction to this note.
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  • 107
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1307-1319 
    ISSN: 0271-2091
    Keywords: Peaceman-Rachford ADI method ; SOR method ; Oseen approximation ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The Navier-Stokes equations, which are the governing equations for a steady, viscous, incompressible fluid rotating about the z-axis with angular velocity ω, are linearized using the Oseen approximation. Two parameters, namely the Reynolds number Re = Ua/v and Reω = 2ωa2/v (the Reynolds number w.r.t. rotation), enter the linearized equations. These equations are solved by the Peaceman-Rachford ADI method and the resulting algebraic equations are solved by the SOR method. Streamlines are plotted and compared with the Oseen solution for the non-rotating case. The magnitude of the vorticity vector with increasing θ is also plotted.
    Additional Material: 11 Ill.
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  • 108
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1381-1394 
    ISSN: 0271-2091
    Keywords: Heat exchangers ; Crossflow ; Tube bundle ; Nusselt number ; Streamfunction/vorticity ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A numerical scheme is developed to predict the heat transfer and pressure drop coefficients in flow through rigid tube bundles. The scheme uses the Galerkin finite element technique. The conservation equations for laminar steady-state flow are cast in the form of streamfunction and vorticity equations. A Picard iteration method is used for the solution of the resulting system of non-linear algebraic equations. Results for the heat transfer and pressure drop coefficients are obtained for tube arrays of pitch ratios of 1·5 and 2·0. Very good agreement of the present results and experimental data obtained in the past is observed up to Reynolds numbers of 1000. It is also observed that the results of the present method show better agreement with the experimental data and that they are applicable for higher Reynolds numbers than results of other studies.
    Additional Material: 11 Ill.
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  • 109
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1269-1283 
    ISSN: 0271-2091
    Keywords: Euler equations ; Real gases ; Local parametrization of the equation of state ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: An efficient algorithm is presented for the solution of the Euler equations of gas dynamics with a general convex equation of state. The scheme is based on solving linearized Riemann problems approximately, and in more than one dimension incorporates operator splitting. In particular, only one function evaluation in each computational cell is required by using a local parametrization of the equation of state. The scheme is applied to two standard test problems in gas dynamics for some specimen equations of state.
    Additional Material: 7 Ill.
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  • 110
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1221-1234 
    ISSN: 0271-2091
    Keywords: Biharmonic equation ; Stokes flow ; Simple layer potential ; Method of fundamental solutions ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: A novel formulation of the method of fundamental solutions for the numerical solution of plane biharmonic problems, based on the simple layer potential representation of Fichera, is presented. The applicability and accuracy of the method are demonstrated by examining its performance on a set of practical problems arising in Stokes fluid flow.
    Additional Material: 9 Ill.
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  • 111
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1487-1501 
    ISSN: 0271-2091
    Keywords: Viscoelastic fluid ; Polymer flow ; Velocity correction method ; Two-step explicit scheme ; Pressure boundary condition ; Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The effects of non-Newtonian behaviour of a fluid and unsteadiness on flow in a channel with non-uniform cross-section have been investigated. The rheological behaviour of the fluid is assumed to be described by the constitutive equation of a viscoelastic fluid obeying the Oldroyd-B model. The finite element method is used to analyse the flow. The novel features of the present method are the adoption of the velocity correction technique for the momentum equations and of the two-step explicit scheme for the extra stress equations. This approach makes the computational scheme simple in algorithmic structure, which therefore implies that the present technique is capable of handling large-scale problems. The scheme is completed by the introduction of balancing tensor diffusivity (wherever necessary) in the momentum equations. It is important to mention that the proper boundary condition for pressure (at the outlet) has been developed to solve the pressure Poisson equation, and then the results for velocity, pressure and extra stress fields have been computed for different values of the Weissenberg number, viscosity due to elasticity, etc. Finally, it is pertinent to point out that the present numerical scheme, along with the proper boundary condition for pressure developed here, demonstrates its versatility and suitability for analysing the unsteady flow of viscoelastic fluid through a channel with non-uniform cross-section.
    Additional Material: 6 Ill.
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  • 112
    Electronic Resource
    Electronic Resource
    Chichester : Wiley-Blackwell
    International Journal for Numerical Methods in Fluids 9 (1989), S. 1539-1542 
    ISSN: 0271-2091
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 113
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989) 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 114
    ISSN: 0192-253X
    Keywords: Oogenesis ; Eggshell ; Gene family ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: This study isolated cDNA clones from egg-chamber and adult female Drosophila cDNA libraries using as probe a DNA fragment from a 200-kb “chromosome walk” in region 32E of the second chromosome of D. melanogaster. The present authors believe that these clones correspond to a new vitelline membrane protein (VMP) gene because (1) cDNA clones in Northern blots identify a transcript expressed in a tissue- and stage-specific manner: stage 10 egg-chambers; (2) the sequence of cDNAs and of the genomic subclone shows homology with the other VMP genes that have been identified to date; (3) the amino acid composition of the translational product has the high content of proline and alanine characteristic of VMPs. Two aspects emerging from this study are worth stressing: (1) the presence of a hydrophobic domain that is highly conserved in all the VMP genes; and (2) the particularly narrow period of expression of the isolated gene, which could be related to the mechanism of vitelline membrane assembly.
    Additional Material: 8 Ill.
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  • 115
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989) 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Type of Medium: Electronic Resource
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  • 116
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    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989), S. 63-69 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Additional Material: 1 Ill.
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  • 117
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989), S. 70-86 
    ISSN: 0192-253X
    Keywords: Arrested cleavage ; Centrosome ; contractile ring ; Fusome ; Germarium ; Models of dividing cells ; Oocyte/nurse cell syncytium ; Ovarian tumor mutation ; POlytrohic meroistic ovary ; Ring canal ; Spindle elongation ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Three-dimensional models were constructed utilizing the information gained from electron micrographs of serial sections of two clones of cystocytes undergoing their terminal divisions. In each clone a polyfusome connected all eight cystocytes together. Each of the spindles was oriented so that one pole touched the polyfusomes, while the other pointed away from it. This positioning of spindles ensures that one cell of each dividing pair retains all previously formed canals, while the other receives none. The two cells that eventually come to contain the maximum number of canals and fusomal material are the ones that differentiate as pro-oocytes, while the others become nurse cells. The orientation of each spindle suggests that the polyfusome formed at one division determines the placement of the cytoskeletal fibers that anchor the spindles formed at the next division. There is a centripetal gathering together of new canals following each cycle of cystocyte division, which is thought to result from the subsequent contraction of the polyfusomal system. Females homozygous for the otu1 mutation are characterized by ovarian tumors, which result when germarial cystocytes undergo supernumerary divisions and fail to differentiate into either nurse cells or oocytes. An analysis of electron micrographs taken of serially sectioned, mutant germaria showed that most germ cells were single or belonged to clusters of two or three interconnected cells. Therefore otu1 cystocytes are unable to undergo a sustained series of arrested cleavages. These cystocytes contain fusomal material that shows ultrastructural differences from normal polyfusomes. We conclude: (1) that a normal polyfusomal system is a necessary prerequisite for the production of a branched chain of cystocytes and for their subsequent differentiation into pro-oocytes and nurse cells; and (2) that a product encoded by the otu+ gene is essential for the construction of a functional polyfusome.
    Additional Material: 16 Ill.
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  • 118
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989) 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 119
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989), S. 123-123 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 120
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989), S. 124-142 
    ISSN: 0192-253X
    Keywords: Cell determination in Drosophila ; Pair-rule gene expression ; Negative transcription control ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The pair-rule genes hairy, runt, even-skipped, and fushi tarazu express their mRNAs and proteins in striped patterns in the Drosophila embryo at the blastoderm stage. Previous studies have shown that the generation of these patterns depends upon products of the gap genes and upon interactions between the pair-rule genes themselves. Here we show that blocking protein synthesis induces expression of each of the pair-rule mRNAs in virtually all regions of the embryo. Our observations together with genetic studies carried out in other laboratories suggest that negative feedback between the pair-rule genes plays a key role in striped expression of pair-rule genes. We propose that stable proteins, present in all regions of the embryo, first activate transcription ofthese pair-rule genes constitutively. Then, various combinations of unstable proteins repress their transcription in a patterned fashion; each stripe of accumulated products of a given pair-rule gene marks a region where it was not repressed. We develop this idea in mathematical form and demonstrate that a network of mutual repression by pair-rule genes can make each blastoderm nucleus into a genetic switch with two stable states. If preexisting gap gene patterns provide initial bias to the blastoderm nuclei, then the “bistable switch behavior” of the nuclei can refine an initially weak spatial bias into a final pattern of sharp stripes.
    Additional Material: 14 Ill.
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  • 121
    Electronic Resource
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    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989), S. 143-154 
    ISSN: 0192-253X
    Keywords: Alternative splicing ; Drosophila development ; Sex determination ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The transformer gene is one of a set of regulatory genes that form the hierarchy controlling all aspects of somatic sexual differentiation in Drosophila melanogaster. The gene transformer occupies an intermediate position in this hierarchy. Analysis of this gene has allowed us to determine the mechanism by which it is regulated in a sex-specific manner and to examine the way in which the regulatory hierarchy is organized. The female-specific expression of the tra gene, previously inferred from genetic observations, is bused on sex-specific alternative splicing of tra pre-mRNA and is not the result of sex-specific transcriptional activation. The female-specific RNA produced by this alternative splicing is the functional mediator of tra activity. Multiple genetic, molecular, and transformation experiments show that female-specific activation of genes or gene products occurs in the order Sex lethal 〉 transformer 〉 transformer-2 〉 doublesex · intersex 〉 female differentiation. The results do not distinguish the level at which transformer might regulate the downstream gene transformer-2. Neither transformer nor any of the downstream genes feedback on, or participate in, alternative splicing of transformer RNA. The mechanism by which Sex lethal regulates transformer splicing appears to be a repression of the use of one of a pair of splice acceptor sites.
    Additional Material: 8 Ill.
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  • 122
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    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989), S. 287-291 
    ISSN: 0192-253X
    Keywords: Robertsonian translocation chromosomes ; Lens ; Optic cup ; Triplication of chromosomes ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Trisomic animals produced from mice doubly heterozygous for Robertsonian translocation chromosomes [Rb(1.3)/Rb(1.10)] consistently show eye defects (e.g., aphakia, micro-phakia, and retention of lens stalk). To determine if changes in distribution or composition of extracellular matrix material may be a factor in development of these defects, eye structures of tnsomy (ts) 1 embryos and normal littermates were studied his-tochemically using the following methods: Alcian blue 8GX, pH 2.5; periodic acid-Schiff (PAS), Alcian blue/PAS combined; high-iron diamine (HID); and HID/Alcian blue combined. Eye development was divided into stages to account for the known delay in ts 1 mouse development.Differences were found in staining patterns as early as stage 1. In later stages, the most consistent difference was an increased period of contact between lens and optic cup due to retardation of interface matrix dissolution between these rudiments in ts 1 embryos. Eyes in which this occurred had abnormally shaped lenses. Overall, the ts 1 optic cup appeared to have fewer staining abnormalities and dysmorphology than did the lens or interface matrix.Triplication of a chromosome may indirectly alter temporal and spatial organization of extracellular matrix through action on cells responsible for the production of this material. Possible mechanisms of action are discussed.
    Additional Material: 2 Ill.
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  • 123
    ISSN: 0192-253X
    Keywords: 5-Azacytidine ; DNA methylation ; Plant tumorogenesis ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: The phenomenon of habituotion is considered in plant tissue cultures to be a real process of chemical tumorogenesis: the cultures acquire the capacity of autonomous growth in a hormone-free medium under the influence of a variety of chemical and physical agents. Treatments with 5-azacytidine (AzaC) of in vitro cultured cells of the Nicotiana glauca × N. langsdorffii nontumorous hybrid (NNT)during the culture cycle led to the induction of a habituated phenotype. The repetitive DNA sequences showed a significant lower level of endogenous methylation in the treated cells in comparison with the normal ones. It is worth noting that it was impossible until now to habituate this strain by conventional methods and that the treatments were effective only in the first 5 days of subculturing; various evidence (cytological and biochemical) pointed out a phenomenon of DNA amplification, occurring in the same period. Moreover, analysis of DNA from control and treated cells shows the induction of variations in the endogenous methylation pattern by AzaC in a critical period of cell culture. These results suggest that demethylation can act as a switch from hormone-dependent to autonomous proliferation by activation of genes coding for or regulating the synthesis of growth factors.
    Additional Material: 6 Ill.
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  • 124
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    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989), S. 304-310 
    ISSN: 0192-253X
    Keywords: Maize ; Catalase ; Kernel ; Gene expression ; mRNA ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In maize three isozymic forms of catalase, CAT-1, CAT-2, and CAT-3 are encoded by three distinct and unlinked structural genes (Catl, Cat2, and Cat3). Catalase activity profiles and zymogram analysis were used to examine the spatial and temporal expression of the three genes during kernel maturation. Three developmental stages of catalase expression were observed in the growing kernel. During stage 1 (6-12 days after pollination), both Catl and Cat3 were expressed; during stage 2 (15-18 days after pollination) only Cat1 expression was observed; and during stage 3 (21-30 days after pollination), Cat1 and Cat2 were expressed. The major constituent tissues of the kernel were examined to determine their contribution to total kernel catalase expression. Each of the tissues was found to have a unique pattern of catalase gene expression. RNA blot analysis, using catalase gene-specific nucleic acid probes, suggests that the differential expression of the three catalase genes observed in the kernel is regulated by controlling the distribution of steady-state mRNA species for the three genes.
    Additional Material: 6 Ill.
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  • 125
    ISSN: 0192-253X
    Keywords: Mouse embryos ; Gap junctions ; Connexin43 ; mRNA ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Gap junctions appear de novo during compaction in the eight-cell stage of mouse development. This is a critical event in the life of the embryo, because gap junctional intercellular communication is an essential requirement for maintaining compaction and, hence, for development of the blastocyst. Recently, a family of genes encoding gap junction proteins (connexins) has been identified and cloned, and we have taken advantage of the availability of antibodies and cDNA probes to investigate the expression of these genes in early development. We found that a protein with antigenic and size similarity to the “liver” gap junction protein, connexin32, is present throughout preimplantation development from the zygote through the late morula. Connexin32 mRNA, however, could not be detected in any preimplantation stage. This, and the presence of connexin32 in zygotes before activation of embryonic transcription, leads us to conclude that this protein is inherited as an oogenetic product that persists well beyond the transition from the oogenetic to embryonic program of gene expression. Furthermore, we found that mRNA for another gap junction protein, connexin43, is fairly abundant in preimplantation embryos. We conclude that it is more likely connexin43, and not connexin32, that is used to assemble new connexons as the level of intercellular coupling increases after compaction.
    Additional Material: 4 Ill.
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  • 126
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    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989), S. 311-317 
    ISSN: 0192-253X
    Keywords: β-globin ; Human erythroleukemia cells ; RNA transcripts ; K562 ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Previous studies have indicated that control and hemin-treated human eryth-roleukemia K-562 cells fail to produce adult-type β-globin mRNA transcripts and to translate them into nascent β-globin chains. Expression of the β-globin DNA sequences in K-562 cells can occur, however, under certain conditions. To readdress this issue and to examine the possibility of whether these cells produce immature and untranslatable β-globin RNA transcripts, we prepared total cyto-plasmic RNA from control and inducer-treated cells and performed Northern blot hybridization analysis using 5′ end-labeled fragments of the human β-globin DNA rather than 3′ end fragments as probes. Although hybridization of both cytoplasmic and nuclear K-562 RNA with a32P-labeled 3′ end fragment (1.6kb Bam H1 cut) coding for a large part of the first exon of β-globin failed to detect β-globin RNA transcripts, hybridization with a 5′ end 32P-labeled 2.0kb Bam H1 fragment (coding for the third exon and part of the second) revealed the presence of relatively small (〈7S) RNA molecules both in nuclear and cytoplasmic fraction. S1 nuclease mapping of both cytoplasmic and nuclear RNA with the use of 5′ end-labeled 2.0 kb Bam H1 fragment of human β-globin DNA indicated protection of a small portion located 64bp 5′ upstream from the Bam H1 site of the second exon. The amount of protected portion was relatively higher in K-562 cells undergoing erythroid maturation. These findings suggest that control and differentiating K-562 cells synthesize β-globin-like RNA transcripts that are 3′ end short, immature, and unable to give rise to adult β-globin chains. These results also indicate that K-562 cells may lack factors that are unique for transcription and processing of the human β-globin RNA transcripts.
    Additional Material: 3 Ill.
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  • 127
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    Chichester [u.a.] : Wiley-Blackwell
    Developmental Genetics 10 (1989), S. 324-332 
    ISSN: 0192-253X
    Keywords: Heat-shock proteins ; Pollen ; Development ; Maize ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: In contrast to sporophytic tissues, mature pollen of higher plants does not synthesize the typical set of heat-shock proteins (HSPs) in response to a marked temperature upshift. Immature grains, however, seem able to do so, at least partially. We investigated the characteristics of HSP synthesis throughout the male gametophytic phase in maize and compared gametophytic and sporophytic heat-shock responses. One-dimensional Sodium dodecyl sulfate-polyacryl-amide gel electrophoresis technique (SDS-PAGE) of newly synthesized proteins revealed that immature pollen synthesizes HSPs, some of which are not induced in sporophytic tissues. The heat-shock response appeared to be related to microgametophytic developmental stages. The strongest response was found in uninucleate microspores: at this stage, in addition to the sporophytic 102, 84, 72, and 18 kD HSPs, three other polypeptides of 74, 56, and 46 kD were observed. In the binucleate and trinucleate stages, only a reduced synthesis of few HSPs could be induced, and differences between genotypes were observed. In germinating pollen, HSP synthesis was not induced under a voriety of heat-stress conditions; however, the consti-tutive synthesis of two polypeptides of the same molecular weight, 72 and 64 kD, as two HSPs was observed. The biological significance of these results is discussed.
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    Developmental Genetics 10 (1989), S. 333-338 
    ISSN: 0192-253X
    Keywords: Cell migration ; Aphidicolin ; Blastula-Gastrula ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: Inhibition of DNA replication by aphidicolin in the chick morula interferes with its progression to a normal blastula and prevents induction of the first morphogenetic cell movements of primitive streak formation. Embryos in aphidicolin synthesize some polypeptides typical of blastula but do not display all the characteristic features of morula to blastula transition. Inhibition of DNA replication inteferes with the sequential synthesis of maternally coded polypeptides and with the activation of the embryonic genome in the chick embryo.
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  • 129
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    Developmental Genetics 10 (1989), S. 345-345 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 130
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    Developmental Genetics 10 (1989), S. 347-347 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 131
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    Developmental Genetics 10 (1989) 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 132
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    Developmental Genetics 10 (1989), S. 339-344 
    ISSN: 0192-253X
    Keywords: Delayed processing ; Splicing ; Transcription ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: This study deals with the pattern of developmental expression of the catalase gene in mice. We have used a mouse catalase 2 kb cDNA (pMCT-1) and its 1.4 kb 5′ fragment as probes to characterize the transcripts during embryonic development and differentiation. Total RNA was isolated from 8 days postconceptus (p.c.) whole embryos and from livers and carcasses of 13, 15, and 18 day p.c. embryos as well as from the livers of newborn and adult mice of the S.W. strain. The RNA was applied on slot blots, and run on agarose gels to generate northern blots. Blots were hybridized with the 32P-labeled cDNA probe under different stringency conditions. Autoradiograms were scanned with a densitometer to quantify relative hybridization signals of RNA samples obtained from two or three individual mice representing each stage of development.The catalase transcript is detectable as early as 8 days p.c. with the beginning of somite formation. At this stage, it is primarily in the form of a 12.2 kb transcript. One additional band (2.4 kb) is also apparent at this stage although at a very low intensity. The intensity of the two bands increases with development, particularly during 13-18 days p.c. in liver and carcass. The 2.4 kb RNA band increases sharply from day 8 through 13, 15, and 18 days p.c. and is confined primarily to the liver. Interestingly, only the 2.4 kb RNA band is seen at and after birth. The 2.4 kb RNA is the known mature message of the catalase gene in mice. The presence of large catalase-specific RNA species (seen during development in utero only) is interpreted as the primary transcript of this gene. The complete and efficient processing of this primary transcript takes place only after birth and primarily in the liver, which may be related to the physiological role of this enzyme in oxygen metabolism, particularly stressful superoxides, expected with independent respiration. At a lower stringency wash of the northern blots, a 9.5 kb RNA was seen during a narrow window of in utero development. This 9.5 kb band may represent an uncharacterized catalase-related gene with a possible role in development and differentiation.
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  • 133
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    Developmental Genetics 10 (1989), S. 349-355 
    ISSN: 0192-253X
    Keywords: SV40 promoter ; Expression vector ; Drug resistance ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have previously demonstrated systemic resistance to methotrexate (MTX) in transgenic mice carrying a foreign, mutant dihydrofolate reductase (DHFR, E.C. 1.5.1.3) gene. The new gene was introduced as a cDNA cloned into an expression vector driven by the simian virus 40 (SV40) early promoter. Previous physiologic studies suggested that transgenic mice tolerated drug doses invariably lethal to controls on the basis of gastrointestinal (GI) resistance to MTX. In the present study we evaluated foreign gene expression at the RNA level in the three major sites of MTX toxicity: intestine, liver, and bone marrow.The transgene was transcriptionally active in small bowel, and levels of expression were high in animals tolerating the largest doses of MTX. The gene was also expressed in the liver in some pedigrees, but was not detected in hemopoietic tissues of any of the pedigrees tested. Our studies correlate the site of expression of a drug resistant dhfr gene with an altered physiologic response to MTX, and demonstrate that transgenic mice can be used as a test system for expression of genes considered for use in somatic gene therapy.
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  • 134
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    Developmental Genetics 10 (1989), S. 356-364 
    ISSN: 0192-253X
    Keywords: Glucose intolerance ; Insulin resistance ; Diabetes mellitus ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We are investigating human insulin gene expression in transgenic mice. An 8.8 kilobase (kb) human genomic DNA fragment, including the insulin gene (1.4 kb) and 2 kb of 5′ human flanking sequences, was introduced into mouse embryos by pronuclear microinjection. Two lines of transgenic mice have been established, both of which carry the intact human gene in multiple copies. Animals from both lines have significantly higher insulin levels than control mice, and the degree of hyperinsulinemia shows a positive correlation with human gene copy number in the two lines. Expression of the human gene is confirmed by the detection of human C-peptide in plasma. Tissue specificity of expression is maintained, with human insulin mRNA detectable only in the pancreas. The transgenics maintain normal fasting blood glucose in spite of their high insulin levels, but preliminary studies show them to be glucose intolerant when given a glucose load. These mice provide a model system for further studies on the regulation of insulin gene expression and on the effects of chronic hyperinsulinemia on glucose homeostasis.
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  • 135
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    Developmental Genetics 10 (1989) 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
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  • 136
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    Developmental Genetics 10 (1989), S. 411-411 
    ISSN: 0192-253X
    Keywords: Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 137
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    Developmental Genetics 10 (1989), S. 402-410 
    ISSN: 0192-253X
    Keywords: F9 ECC ; Aggregates ; Embryoid bodies ; Endoderm ; Life and Medical Sciences ; Genetics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: To study the relationship between compaction and differentiation in aggregates of F9 embryonal carcinoma cells, a subline was developed which grows mostly uncompacted in monolayer culture in medium containing a low concentration of calcium (about 0.05 mM). When these cells were trypsinized and cultured in suspension in the same medium, they formed loose, open aggregates, which failed to differentiate into embryoid bodies after exposure to 10 nM retinoic acid, confirming the requirement of compaction for differentiation. If, after culture for 3 days, the uncompacted F9 aggregates were exposed to additional calcium (4 mM), all compacted within an hour. The number of days necessary for aggregates to acquire this ability to compact rapidly was reduced if the monolayer of cells from which the aggregates were derived had been exposed to additional calcium to cause compaction for several days prior to trypsinization and aggregation. Next, treatment of the compacted F9 aggregates with 10 nM retinoic acid was followed by differentiation into embryoid bodies. The number of days required for this was also reduced if the aggregates were formed from previously compacted cells, presumably because compaction of the aggregates occured sooner.The acceleration in compaction and differentiation in aggregates formed from previously compacted cells suggests that some of the proteins important for compaction, which are synthesized in a monolayer of compacted cells, persist through trypsinization and are carried over from monolayer to aggregates. Alternatively, an inhibitor of compaction is decreased in the compacted monolayer. Thus, the process of compaction in its entirety, including its relationship to subsequent differentiation, cannot be studied in aggregates formed from F9 cells grown as usual in the compacted state in monolayer culture. This work provides an alternative system in which aggregation, compaction, and differentiation of F9 cells can be made to occur in stepwise fashion and can be examined separately.
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  • 138
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 145-152 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A two-dimensional finite difference alternating direction implicit (ADI) scheme numerical model to solve the vertically integrated form of the non-linear hydrodynamics equations and convection-diffusion equation has been developed for the description of tide flow and pollutant transport in Taipong Bay, China. Computer software for the modelling is well designed to reduce storage and costs of computation. The computed results agree quite well with the observations available. The tidal level, tidal current, residual current and organic pollution in the bay are discussed based on the computed results and observed data. Applications for the environmental problems along the coast of the bay are also mentioned briefly.
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  • 139
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 195-213 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Consolidation problems associated with foundations for off-shore structures are described and analysed using the finite element method. The structure itself and the soft underlying soil are modelled by finite elements with different constitutive relationships for each. Interfacial behaviour between the two is simulated by six-noded elements, with a hyperbolic stress-strain relationship.Having modelled the soil-structure system behaviour during the consolidation stage, a soil-structure interaction analysis is then carried out for both shallow and deep foundations. Other important factors, such as the redistribution of stresses in the structure itself which have resulted from differential settlements, will also be investigated.
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  • 140
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 271-283 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Damage generally refers to the more or less gradual development of micro-voids and micro-cracks. Damage mechanics is the modelling of these phenomena on a structural analysis scale. In this paper we first recall the non-linear behaviour models we have developed to model composite laminates. Then we present two examples of implementations of such models in a structural analysis code in order to simulate the inner-failure of a structure, or to study delamination initiation.
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  • 141
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 299-321 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The stiffness matrix of a beam made of composite superconductor elements is derived. The effects of friction between conductors through the insulation layers are taken into account. Furthermore, the effects of strand transposition of the wires, already studied by the authors, are included in the model.Some applications of the proposed approach to superconductor layouts proposed for the NET (Next European Torus) toroidal and poloidal field coils are shown. These indicate that the effects of slip are not negligible and should be taken into account in a more reliable structural analysis of the coil system. Parametric studies with varying width and heights of the insulation layer have been also carried out and the corresponding diagrams are shown here.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 383-401 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A review is given of recent advances in two aspects of the numerical simulation of the buckling and postbuckling responses of composite structures. The first aspect is exploiting non-traditional symmetries exhibited by composite structures; and strategies for reducing the size of the model and the cost of the buckling and postbuckling analyses in the presence of symmetry-breaking conditions (e.g. asymmetry of the material, geometry, and/or loading). The second aspect pertains to the prediction of onset of local delamination in the postbuckling range and accurate determination of transverse shear stresses in the structure. The accuracy and effectiveness of the strategies developed are demonstrated by means of a numerical example.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 453-453 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 144
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    International Journal for Numerical Methods in Engineering 27 (1989) 
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    Keywords: Engineering ; Engineering General
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 501-522 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: We used a conjugate gradient type method, with preconditioning, to solve the sparse linear systems arising from the discretization of PDEs. With such methods, the main obstacles for complete vectorization have been the preconditioning calculation and its application step within the iteration: for the matrices obtained using 5- or 9-point discretization operators, some well known existing preconditionings (like ILU) require a block-recursive procedure which prevents vectorization. Preconditioners based on nested incomplete factorization, which require the calculation of approximate inverses of tridiagonal matrices, allow complete vectorization of the application step. We present a formulation of such a preconditioning, using a Frobenius norm minimization to calculate the inverses, which also allows complete vectorization of the inverses' calculation, thus making the iterative solver completely vectorizable. Numerical experiments show that the method is robust over a range of symmetric and non-symmetric problems, and up to 4 times faster than other existing methods, such as ILU, depending on the computer and compiler being used. We also show the importance of diagonal scaling used in conjunction with other preconditionings and present some theoretical results concerning the approximate inverses of tridiagonal matrices, calculated using the Frobenius norm minimization.
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  • 146
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 571-588 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: ITPACK 2C14 is a package of seven iterative algorithms for solving sparse linear systems represented by Au = b, where A is symmetric and positive definite or mildly non-symmetric. This paper describes the techniques used to vectorize the iterative algorithms in the ITPACK 2C package for the Cyber 205 and Cray X-MP vector computers. The resulting package was named ITPACKV 2C.15 The basic iterative methods in ITPACK 2C are described in terms of matrix-vector multiplications and forward and backward solutions, and the techniques used in the vectorization of these and other computational kernels are given. Results of experiments using ITPACK 2C and ITPACKV 2C are given, including a comparison of megaflop rates and timings for two model problems.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 589-608 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: NSPCG is the most recent research-oriented software package developed as part of the ITPACK Project at the Center for Numerical Analysis of The University of Texas at Austin. It is designed to solve large sparse systems of linear equations by a variety of different non-symmetric preconditioned conjugate gradient methods. Several different sparse data storage schemes are available for storing the coefficient matrix of the linear system. Matrices with a wide range of structures from highly structured to completely unstructured can be accommodated. To limit memory requirements, the accelerators in the package can be called directly with the matrix stored in a user-defined sparse data storage format (for example, from a particular application) by supplying some user-written routines for certain matrix-vector operations.The main entry point into the package is through a single subroutine call. The various methods are accessed by using a particular naming convention for the first two parameters that in turn selects a preconditioner, an accelerator and a data storage scheme. Some of the basic preconditioners that are available are Jacobi, Incomplete LU Decomposition and Symmetric Successive Overrelaxation as well as block preconditioners. The user can select from a large collection of accelerators such as Conjugate Gradient (CG), Chebyshev (SI, for semi-iterative), Generalized Minimal Residual (GMRES), Biconjugate Gradient Squared (BCGS) and many others. The package is modular so that almost any accelerator can be used with almost any preconditioner. One of the main purposes for the development of the package was to provide a common modular structure for research on iterative methods. The entire package is written in Fortran 77 with vectorization in mind for applications on supercomputers.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1-11 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The numerical integration of the rate equation of an elastic-plastic material is considered. Special attention is focused on the discretization via the fully implicit backward Euler method in the small strain case with linear elasticity and the yield function a general quadratic in stress space. Here the calculation of the plastic (Lagrange) multiplier reduces to the computation of the smallest positive root of a polynomial in one variable. Explicit formulae are given for some special cases.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 145-154 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Based on purely kinematical considerations the possibility of inextensional bending is introduced to isoparametric curved C° elements, which, otherwise, are plagued by severe membrane (and shear) locking. The analysis is restricted to arches and axisymmetric deformations of shells, i.e. kinematically two-dimensional problems. The results show exceptionally good accuracy. High reliability of the approach is guaranteed by absence of spurious kinematic modes on the element level, which complements its ability to bend inextensionally (in the case of arches).
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 193-209 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A phase increment method is introduced to construct the response curves for the damped Duffing oscillator in primary, superharmonic, and subharmonic resonances. Non-linear parameters can be arbitrarily large. The algorithm is numerically stable. All resonance response curves are constructed in a unified manner. Closed loop curves are obtained in subharmonic resonances as opposed to open ended ones predicted by the perturbation method. Higher order resonances are constructed without difficulties. Loops are also observed in superharmonic resonances when non-linearity is not small.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 241-244 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1485-1485 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1487-1504 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The presented work addresses the relationships between optimal sampling points, reduced integration and geometric distortion with the objective of estimating errors in terms of those considerations. Isoparametric quadratic plane and solid elements are used as a vehicle for the study. Geometric distortion measures and evaluation conditions, based on convergence requirements, are first defined in terms of the polynomial orders of the geometry and applied strain. Using these, the concept of optimal stress sampling, already established for undistorted elements, is extended to distorted geometry and shown to be effective over a range of geometries and strains. Errors in the strain-displacement relationship and numerical integration of the strains are used to estimate the total response error and to rationalize the connection between optimal stress points and reduced integration. Enhanced convergence, by extension to the representation of linear strains in elements with quadratic geometry, is identified as the main advantage of reduced integration. The applicability of the proposed, and other, distortion parameters to vetting of element geometry and error prediction is discussed.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1567-1576 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In the Part I companion paper, various PCG (preconditioned conjugate gradient) strategies for solving the first order time dependent problem Mu̇ + Ku = f were compared. In all cases M was assumed to be the consistent ‘mass’ matrix arising out of conventional finite element semi-discretization of the partial differential equation, and not its lumped approximation. In the present paper, similar PCG strategies are applied to the second order time dependent problem Mü + Cu̇ + Ku = f. Again consistent M and C can be retained. Various global and element level preconditioners are compared and optimized.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1645-1660 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This article presents a shooting-type numerical procedure for the analysis of a planar, continuous and flexible member where the material is permitted to unload and reload plastically. A kinematic type of strainhardening rule is employed, and large displacements, large rotations and general cross section shapes are admitted. Though numerical and semi-analytical solutions exist in the literature for specific problems where the internal and external loads increase monotonically (see, for example, References 1-4), little attention has been paid to problems where these loads (specifically internal loads) are permitted to decrease or reverse direction. In the present work a comparison is made with the solution to one such problem found in the literature, and the solution to four additional problems is given to show the versatility and usefulness of the method.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 980-980 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1041-1060 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A decomposition technique for alternative loading conditions in the integrated optimal structural design is developed. The method, called the move coordination, consists of partitioning the large structural optimization problem into a set of smaller coupled subproblems. In each subproblem only one loading condition is considered and the subproblems are solved in a parallel cyclic way. The coupling among the subproblems is accomplished through the introduction of coordinating constraints between each subproblem. These constraints ensure that the final design is the same and feasible for all subproblems. The method developed is illustrated by two examples of member sizing of truss structures using the integrated optimal design formulation and geometric programming. The method presents the advantage of reducing the size of the optimization problem as well as the computer processing time. The method is also suitable for implementation on computers using parallel processing.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1023-1040 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An operator-splitting algorithm for the two-dimensional convection-dispersion-reaction equation is developed. The flow domain is discretized into triangular elements which are fixed in time. The governing equation is split into three successive initial value problems: a pure convection problem, a pure dispersion problem and a pure reaction problem. For the pure convection problem, solutions are found by the method of characteristics. The solution algorithm involves tracing the characteristic lines backwards in time from a vertex of an element to an interior point. A cubic polynomial is used to interpolate the concentration and its derivatives on an element. For the pure dispersion problem, an explicit finite element algorithm is employed. Analytical solutions are obtained for the pure reaction problem. The treatment of the boundary conditions is also discussed. Several numerical examples are presented. Numerical results agree well with analytical solutions. Because cubic polynomials are used in the interpolation, very little numerical damping and oscillation are introduced, even for the pure convection problem.
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  • 159
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1115-1129 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The NONSS method for numerically integrating time-dependent constitutive equations requires evaluation of the partial derivatives of the constitutive equations. A numerical method for evaluating these partial derivatives has been developed, thus avoiding the cumbersome task of analytically re-deriving the partial derivatives when improvements to the constitutive model are evaluated. This method is based upon the adaptive finite-difference algorithm published by Stepleman and Winarsky. Modifications of their algorithm are described that allow its efficient use within an extended version of NONSS, called NONSS-ND.Using the MATMOD constitutive equations, the capabilities of NONSS-ND are demonstrated by comparing the results of a wide variety of deformation simulations with those of NONSS, for which the derivatives are computed from analytical solutions. The numerical differentiation within NONSS-ND is shown to be sufficiently accurate for use in integrating time-dependent constitutive equations, but results in a 30-100 per cent increase in computation time. Multi-element structural calculations are therefore found to be uneconomical, but NONSS-ND is well suited for testing alternative constitutive models owing to its accuracy and its general applicability to highly non-linear systems of differential equations.
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  • 160
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 361-382 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Finite element models of the continuum-based theories and two-dimensional plate/shell theories used in the analysis of composite laminates are reviewed. The classical and shear deformation theories up to the third-order are presented in a single theory. Results of linear and non-linear bending, natural vibration and stability of composite laminates are presented for various boundary conditions and lamination schemes. Computational modelling issues related to composite laminates, such as locking, symmetry considerations, boundary conditions, and geometric non-linearity effects on displacements, buckling loads and frequencies are discussed. It is shown that the use of quarter plate models can introduce significant errors into the solution of certain laminates, the non-linear effects are important even at small ratio of the transverse deflection to the thickness of antisymmetric laminates with pinned edges, and that the conventional eigenvalue approach for the determination of buckling loads of composite laminates can be overly conservative.
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  • 161
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1265-1282 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A dynamic programming (DP) method is presented for analysis of statically determinate and indeterminate bridges subjected to moving loads such as those specified by the American Association of State Highway and Transportation Officials (AASHTO) specifications. These loads consist of uniform lane loading, two-axle truck loading and two-axle truck plus one-axle semitrailer loading. The solution of the DP problem is based on the use of influence line diagrams and extremum functions. Recurrence formulae have been developed for various types of AASHTO live loads. The procedure presented in this article is quite general and can be applied to any type of structures with linear behaviour and any type of moving loads. Six examples are presented: a simply-supported beam, a simply-supported Pratt truss, an arch bridge, a continuous Pratt truss, a continuous frame and a cable-stayed bridge.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 547-557 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The Successive Overrelaxation (SOR) and the Cyclic Chebyshev Semi-Iterative (CCSI) methods are considered for solving the non-symmetric linear systems Ax = b when A has the form \documentclass{article}\pagestyle{empty}\begin{document}$$ {\bf A} = \left({\begin{array}{*{20}c} {{\bf D}_1} & {\bf F} \\ {-{\bf F}^{\rm T}} & {{\bf D}_{\rm 2}}\\ \end{array}} \right) $$\end{document} with D1 and D2 symmetric positive definite (SPD).The D1/2-norms of both methods are determined and it is shown that, though the SOR method is better based on the spectral radius, the CCSI scheme is far better than SOR according to the D1/2-norm.
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  • 163
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 623-635 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 28 (1989) 
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 13-25 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In this work, a modal solution method for transient heat conduction utilizing a co-ordinate transformation matrix generated by the Lanczos algorithm is presented. The special characteristics of this co-ordinate transformation are also discussed. The comparisons made in the NASA Insulation Test problem analysis shown that this approach is more cost-effective than direct solutions, without loss of accuracy.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 95-108 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An efficient method is developed for sensitivity analysis in shape optimization of axisymmetric structures. The technique of isoparametric mapping is used to generate the finite element mesh from a small set of master elements and master nodes. Co-ordinates of selected master nodes are used as design variables. Shape function values of master elements at derived finite element nodes obtained during the isoparametric mapping process are utilized to calculate the gradients of weight and response of the structures with respect to the design variables. Analytic formulations of the gradients are developed for sensitivity analysis of axisymmetric structures. An optimization procedure using a sequential linear programming method is applied to effectively utilize the calculated gradients. Numerical examples of optimum design of disks subject to thermo-mechanical loadings are presented.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 155-179 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The paper addresses the question of the accuracy and reliability of the computational analysis of the rhombic plate problem. The Kirchhoff model has a large error (measured in the energy norm) in comparison with the three dimensional solution with a soft simple support; also for very thin plates (t = 1/100a) and all angles (up to α = 90°). The Reissner-Mindlin model gives results 3-5 times better and is less sensitive to the change of the plate angle. The Kirchhoff model is a relatively good approximation of three dimensional setting for a hard simple support. The paradoxical (polygon) behaviour of the simply supported Kirchhoff plate extends to the Reissner-Mindlin model with a hard support. The finite element solution of the Kirchhoff model is addressed in detail. It is shown that higher degree methods are clearly preferable and that the skewness of the elements does not influence essentially the accuracy of the method; the singularity of the solution, which strongly depends on the skewness of the plate, is the primary cause of the deterioration of the performance of the FEM.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 2466-2466 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 28 (1989) 
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 2517-2540 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The problem of static, non-linear, large three-dimensional deformation of riser bundles used in offshore oil and gas production is studied within the limits of small strain theory. The mathematical model consists of the models of component-risers and connectors which hold risers together. Each riser is modelled as a thin walled, slender, extensible or inextensible tubular beam-column. It is subject to non-linear three-dimensional deformation dependent hydrodynamic loads, torsion and distributed moments, varying axial tension, and internal and external fluid forces. The problem is solved numerically by developing an algorithm which features substructuring, condensation and non-linear incremental finite elements. Substructuring is used to decompose the riser bundle problem into those of individual component-risers and equilibria of connectors. Condensation is used along with the connector equilibrium equations to produce connector forces and moments. Strong non-linearities present in the model are handled by an incremental finite element approach. Accuracy of the computer code is verified by solving simple three-dimensional cases. Two three-dimensional applications are solved for a bundle with seven component-risers and up to a total of 1267 degrees of freedom. Finally, a comparison is made with numerical results of a two-dimensional analysis code. The influence of problem size on total CPU time is discussed.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 2609-2634 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The conceptual framework of a least squares rate variational approach to the formulation of continuously deforming mixed-variable finite element computational scheme for a single evolution equation was presented in Part I.1 In this paper (Part II), we extend these concepts and present an adaptively deforming mixed variable finite element method for solving general two-dimensional transport problems governed by a system of coupled non-linear partial differential evolution equations. In particular, we consider porous media problems that involve coupled heat and mass transport processes that yield steep continuous moving fronts, and abrupt, discontinuous, moving phase-change interfaces. In this method, the potentials, such as the temperature, pressure and species concentration, and the corresponding fluxes, are permitted to jump in value across the phase-change interfaces. The equations, and the jump conditions, governing the physical phenomena, which were specialized from a general multiphase, multiconstituent mixture theory, provided the basis for the development and implementation of a two-dimensional numerical simulator. This simulator can effectively resolve steep continuous fronts (i.e. shock capturing) without oscillations or numerical dispersion, and can accurately represent and track discontinuous fronts (i.e. shock fitting) through adaptive grid deformation and redistribution. The numerical implementation of this simulator and numerical examples that demonstrate the performance of the computational method are presented in Part III2 of this paper.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 2709-2710 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 461-474 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A numerical scheme for crack modelling by means of continuous displacement fields is presented. In two-dimensional problems a crack is modelled as a limiting case of two singular lines (with continuous displacements, but discontinuous displacement gradients across them) which tend to coincide with each other. An analysis of the energy dissipated inside the band bounded by both lines allows one to obtain an expression for the characteristic length as the ratio between the energy dissipated per unit surface area (fracture energy) and the energy dissipated per unit volume (specific energy) at a point. The application of these mathematical expressions to the finite element discretized medium allow one to obtain a general spatial and directional expression for the characteristic length which guarantees the objectivity of the results with respect to the size of the finite element mesh. The numerical results presented show the reliability of the proposed expressions.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 476-476 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 175
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 489-509 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An analysis, based on the use of Taylor series expansions, is developed to determine accuracy estimates for derivatives in one and two dimensions computed by differentiation of a finite-element interpolant or approximation. The analysis clarifies some issues concerning special points at which the derivatives are believed to be exceptionally accurate with higher convergence rates (superconvergence). Moreover, it leads directly to a class of post-processing strategies for the derivatives and offers a more direct constructive approach to the subject.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 561-577 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The numerical technique of differential quadrature for the solution of linear and non-linear partial differential equations, first introduced by Bellman and his associates, is applied to the equations governing the deflection and buckling behaviour of one- and two-dimensional structural components. Separate transformations are used for higher-order derivatives, as suggested by Mingle, thus extending the method to treat fourth-order equations and to include multiple, boundary conditions in the respective co-ordinate directions. Results are obtained for various boundary and loading conditions and are compared with existing exact and numerical solutions by other methods. The application of differential quadrature to this class of problems is seen to lead to accurate results with relatively small computational effort.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 621-627 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A collocation method is described which obtains an approximate solution to Poisson's equation, δu = f, on an L shaped region. The L shaped region is viewed as the union of two overlapping rectangles. The Schwarz alternating procedure may be employed to reduce the problem to one in which collocation techniques are used on each rectangle. The convergence of the alternating scheme depends upon a discrete maximum principle for collocation methods. Several sample problems are presented to illustrate the order of convergence of this method and to compare it with several existing numerical methods for the L shaped region.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 679-685 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The Galerkin and subdomain forms of the weighted residual method are used to generate recursive equations in time for the numerical solution of a system of ordinary differential equations. The single-step methods that result from a linear interpolation equation match currently available methods whose stability and oscillation properties are known. A three-level scheme developed by combining two linear elements is shown to be unconditionally unstable. Two of the three schemes obtained using a quadratic interpolation equation and quadratic weighting functions are also shown to be unconditionally unstable. The third scheme is unconditionally stable, but the calculated values for a numerical solution of u̇ + u = 0, u(0) = 1 are not as accurate as the values obtained using the single-step central difference method.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 726-726 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 753-768 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: A method using a material description of the instantaneous configuration, valid for viscoplastic material with large deformations, is presented. In view of numerical tests which were carried out, this material formulation, associated with an implicit integration scheme which proved to be numerically accurate and reliable, is shown to be preferable.An algorithm is developed for resolution of sliding or evolving contact condition problems.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 833-844 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A new method of representing the steei in finite element analyses of reinforced concrete structures is described in which the steel and the concrete are analysed separately. The forces between the steel and concrete are used In an interative method which brings the two solutions together. The method converges very rapidly and it is shown that the computational effort is principally dependent on the mesh chosen for the concrete. All the steel in a reinforced concrete structure may be easily included without affecting the layout of the concrete mesh. Results, which are given for three practical problems, include detailed steel and bond stresses for all bars.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 257-269 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The multilayer degenerated 3-D shell element, for which the stiffness matrix is calculated by numerical integration ply by ply, gives accurate results even for moderately thick composite panels, but needs an important linear and non-linear generation time when the number of plies is high (N 〉 10). In order to reduce this time some pre-integration and homogenization techniques are investigated. Different pre-integration methods have been reviewed and discussed. Then, two new homogenization methods, based on a series expansion of an equivalent Hooke matrix over the thickness, are presented. Next, simple numerical validation tests of these new methods are discussed, indicating necessary further investigations. Finally, a general discussion about the properties of the pre-integration and homogenization techniques tends to define their respective application domain.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1351-1370 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: The paper deals with a new mixed finite element method of solution of the bending problem of clamped anisotropic/orthotropic/isotropic plates with variable/constant thickness. This new mixed method gives simultaneous approximations to displacement u and bending and twisting moment tensor (ψij)1 ≤ i, j ≤ 2. Computer implementation procedures for this mixed method are given along with results of numerical experiments on a good number of interesting problems.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1429-1448 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: In this article a new mesh generation algorithm is presented. The algorithm is based on a new approach called the vertex label assignment scheme to provide the information for the mesh generation so that parallel processing becomes possible. The algorithm generates 2D meshes of quadrilaterals on the basis of individual faces; conformity and smoothness of the resultant mesh are automatically assured. Local and selective mesh-refinements are also supported. A regular quadrilateral network which defines the geometry of the problem and an associated subdivision level assignment which specifies mesh density data on the network are the only input information.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 469-481 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: Piecewise linear finite element approximations to two-dimensional Poisson problems are treated. For simplicity, consideration is restricted to problems having Dirichlet boundary conditions and defined on rectangular domains Ω which are partitioned by a uniform triangular mesh. It is also required that the solutions u ∊ H3 (Ω). A method is proposed for recovering the gradients of the finite element approximations to a root mean square accuracy of O(h2), both at element edge mid-points and element vertices, using simple averaging schemes over adjacent elements. Piecewise linear interpolants (respectively discontinuous and continuous) are then fitted to these recovered gradients, and are shown to be O(h2) estimates for ∇u in the L2-norm, and thus superconvergent. A discussion is given of the extension of the results to problems with more general region and mesh geometries, boundary conditions and with solutions of lower regularity, and also to other second-order elliptic boundary value problems, e.g. the problem of planar linear elasticity.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 609-622 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: When applying an incomplete block-factorization technique one needs sparse approximate inverses of the successive Schur complements computed throughout the factorization. Here we propose a method for the construction of such sparse approximate inverses. The method has an advantage over earlier versions, in that such approximate inverses of block-tridiagonal matrices can be computed in parallel. Comparative numerical experiments for solving a number of discretized diffusion equations by this preconditioning matrix in a preconditioned conjugate gradient method and earlier versions of incomplete block-factorization preconditioners are presented.
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    International Journal for Numerical Methods in Engineering 27 (1989), S. 655-664 
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    Source: Wiley InterScience Backfile Collection 1832-2000
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    Notes: We examine multigrid solution for convection-diffusion problems in which convective effects are significant. In particular, we consider the case where the fine grid satisfies the associated cell or diagonal dominance condition but coarse grid levels violate this condition. Related numerical experiments are conducted. We also introduce an alternative local elliptic projection technique and compare this with interpolating the error corrections from coarse to fine grids. In addition, we demonstrate the use of grid redistribution and optimization techniques in the multilevel context.
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 27-41 
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    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: Owing to the failure of the finite element analyst to employ a properly refined computational model, the accuracy of preliminary finite element computations is often low. Thus, it is useful to introduce a computational procedure for improving the results obtained from a preliminary finite element solution. Such a procedure is presented in this paper. In this procedure the solution error components are decomposed into two parts. One of the error components is assumed to have a long period variation. The other component is assumed to have a short period variation. Multiplicative and additive correction procedures are introduced to iteratively eliminate the two error components. The multiplicative and additive correction procedures are implemented using multi-level solution techniques.
    Additional Material: 14 Ill.
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  • 189
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 109-126 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents the development of a straightforward displacement type triangular finite element for bending of a flat plate with the inclusion of transverse (or lateral) shear effects. The element has twenty two degrees of freedom consisting of ten for the lateral displacement of the midplane and six for rotations of the normal to the undeformed midplane of the plate. The latter are taken as independent of the slopes of the deformed midplane in order to include deformation due to transverse shear. The element is fully conforming and may be orthotropic. At interelement boundaries, the element matches adjacent elements both with respect to lateral displacement of the midplane and the rotations of the normal. The result is an efficient ‘linear moment’ triangular element but with transverse shear deformation included. Numerical computations for a number of examples are presented. The results show the element to be more flexible than most other finite element models and agree closely with those from a numerical solution of the three dimensional elasticity equations. The results also converge to those from thin plate theory when the thickness to length ratio becomes small or when the transverse shear moduli are artificially increased.
    Additional Material: 6 Ill.
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  • 190
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1839-1853 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: In this work we seek to characterize the conditions under which an elastic-plastic stress update algorithm preserves the symmetries inherent to the material response. From a numerical standpoint, the aim is to determine under what conditions a stress update algorithm produces symmetric consistent tangents when applied to materials obeying normality. For the ideally plastic solid we show that only the fully implicit or closest point return mapping algorithm is symmetry preserving. For hardening plasticity, symmetry cannot be preserved in general unless suitable restrictions are imposed on the constitutive equations. We show that these restrictions amount to the existence of a pseudo-internal energy function acting as a joint potential for both the direction of plastic flow and the hardening moduli. In view of the fact that holonomic methods based on incrementally extremal paths also result in update rules possessing a potential structure and, hence, in symmetric tangents, we address the question of whether any connections exist between the two approaches. We show that holonomic methods and the fully implicit algorithm may indeed be brought into correspondence.
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  • 191
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1909-1928 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The applications of the reduced integration technique, and the addition of non-conforming modes and their coupling to Mindlin plate elements to improve their basic behaviour are reviewed and the establishment of a series of new plate elements by combined use of these schemes is presented in this paper. The element formulation is based upon the quadratic Mindlin plate concept. The results obtained by new elements converge to the exact solutions very rapidly as the mesh is refined and show reliable solutions even for severely distorted meshes. The new elements have the requisite numbers of zero eigenvalues associated with rigid body modes to avoid spurious zero energy modes. These elements are shown to solve the shear locking problem completely so that they are applicable to a wide range of plate problems, giving a high accuracy for both thick and thin plates.
    Additional Material: 17 Ill.
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  • 192
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1951-1964 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An attempt has been made to study the influence of large deformation on the stress intensity factor in a cracked plate subjected to bending including shear deformation. It is assumed that singular terms for stress resultants and strains in the case of large deformation have the same angular distribution and order of singularity as in the case of a linear problem. With this in view the small deformation singular element has been used at the crack tip region surrounded by large deformation plate bending elements. The finite element analysis, based on total Lagrangian formulation combined with the modified Newton-Raphson technique, has been used to get numerical results. Several examples connected with large deformation of cracked plates subjected to bending are studied. Using the above technique stress intensity factors for linear and non-linear cases have been compared.
    Additional Material: 9 Ill.
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  • 193
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 1977-1994 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A direct boundary element method is developed for the dynamic analysis of thin elastic flexural plates of arbitrary planform and boundary conditions. The formulation employs the static fundamental solution of the problem and this creates not only boundary integrals but surface integrals as well owing to the presence of the inertia force. Thus the discretization consists of boundary as well as interior elements. Quadratic isoparametric elements and quadratic isoparametric or constant elements are employed for the boundary and interior discretization, respectively. Both free and forced vibrations are considered. The free vibration problem is reduced to a matrix eigenvalue problem with matrix coefficients independent of frequency. The forced vibration problem is solved with the aid of the Laplace transform with respect to time and this requires a numerical inversion of the transformed solution to obtain the plate dynamic response to arbitrary transient loading. The effect of external viscous or internal viscoelastic damping on the response is also studied. The proposed method is compared against the direct boundary element method in conjunction with the dynamic fundamental solution as well as the finite element method primarily by means of a number of numerical examples. These examples also serve to illustrate the use of the proposed method.
    Additional Material: 6 Ill.
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  • 194
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 2219-2222 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 195
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 769-784 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The amount of upwind or magnitude of off-centering needed in the numerical solution of second order differential equations with significant first derivatives is justified more rigorously in this paper by requiring the satisfaction of a variational principle. It will be shown that, for a discrete solution, a set of variational principles can be found which allow the problem to be solved as a self-adjoint system. The technique presented here will give a clear indication of those regions where (i) upwind techniques are not required, (ii) upwind techniques are necessary and sufficient and (iii) upwind techniques are insufficient and artificial viscosity is required.
    Additional Material: 7 Ill.
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  • 196
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 817-832 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper presents a three dimensional algorithm for dynamic Lagrangian computations for solids, with variable nodal connectivity to allow for severe distortions. The nodes are analogous to flexible spheres. When they move closer together than their equilibrium distance they generate compressive, repulsive forces. Conversely, when they move apart, they generate tensile attractive forces. Material strength effects are also included. Because a node can be affected only by its ‘neighbour’ nodes, the approach has been designated the ‘NABOR’ approach. The distinguishing feature of this technique is that it is possible to have variable connectivity. A node can acquire new neighbours, thus allowing all forms of distortion. The three dimensional NABOR algorithm has been incorporated as an option into the explicit finite element code, EPIC-3. By using both the NABOR grid and the traditional EPIC-3 finite element grid together, it is possible to perform Lagrangian computations for a wider range of problems.
    Additional Material: 12 Ill.
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  • 197
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 893-907 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: An implementation of the force method is proposed in which the forces and the displacements are simultaneously obtained by the solution of a sparse symmetric indefinite system. The matrix of coefficients is formed by just the concatenation of the element flexibility and equilibrium matrices. No computational procedure is required to generate the compatibility conditions (or the self-stress matrix) and no partitioning of the force vector is made into a basic set and a redundant set, unlike the conventional force method. A slightly modified sparse unsymmetric system can be written in which the stresses and the displacements are the unknowns. This is used as constraints in the formulation of the minimum weight design problem for large structures under static loading conditions. A sparse generalized reduced gradient package is used as the optimizer. A class of test problems involving large truss structures is solved. The results indicate that the present implementation of the force method is better than the displacement method for the optimum design of large structures.
    Additional Material: 9 Ill.
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  • 198
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 955-965 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A method is presented for determining the natural frequencies and the corresponding mode shapes of isotropic bimodular beams at certain supporting conditions. Although only the lowest three modes of the single-layer and two-layer bimodular beams were studied, in principle, the method may also be used to determine higher-mode natural frequencies and shapes of the multi-layer beams. Numerical analysis shows that the approach is suitable for the free-vibration analysis of clamped/free and hinged/hinged bimodular beams.
    Additional Material: 7 Ill.
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  • 199
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 980-980 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Type of Medium: Electronic Resource
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  • 200
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    International Journal for Numerical Methods in Engineering 28 (1989), S. 987-999 
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The numerical strategies employed in the evaluation of singular integrals existing in the Cauchy principal value (CPV) sense are, undoubtedly, one of the key aspects which remarkably affect the performance and accuracy of the boundary element method (BEM).Thus, a new procedure, based upon a bi-cubic co-ordinate transformation and oriented towards the numerical evaluation of both the CPV integrals and some others which contain different types of singularity is developed.Both the ideas and some details involved in the proposed formulae are presented, obtaining rather simple and-attractive expressions for the numerical quadrature which are also easily embodied into existing BEM codes.Some illustrative examples which assess the stability and accuracy of the new formulae are included.
    Additional Material: 6 Ill.
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