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851.
852.
Several techniques for experimental determination of floating point precision in practical computations are examined, and applied to linear algebra algorithms. These techniques are simple enough to be directly applicable to existing production codes, requiring a very limited amount of software on many machines, and yet they yield interesting information on the numerical precision of a computation. Our choice of linear algebra algorithms includes a direct solver (namely the MA32 program from the Harwell Library) and several variants of preconditioned conjugate gradients (the methods DIAG, INV, MINV and POL of Reference 1). The results may be of interest as method selection criteria, and thus complement Mflop performance data available from several sources. 相似文献
853.
On the basis of the model “polymer chain in an array of obstacles” the influence of the topology effects on the dynamics of concentrated polymer systems is investigated theoretically. The 1/z-expansion (where z is the coordinational number of the lattice of obstacles) is proposed for this problem. By means of this expansion the diffusion coefficient of a linear unclosed polymer chain is calculated. The equilibrium properties of linear closed chain (i.e. ring) unentangled with either of the edges of the lattice are investigated in detail. In particular, it is shown that the diffusion coefficient D of the center of mass of closed chain consisting of N links is proportional to N−5/2. 相似文献
854.
Journal of Applied Spectroscopy - 相似文献
855.
A. M. Panich 《Journal of Structural Chemistry》1989,30(4):679-681
Institute for Inorganic Chemistry, Siberian Branch, USSR Academy of Sciences. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 4, pp. 170–172, July–August, 1989. 相似文献
856.
S. A. Kuliev 《Mechanics of Solids》2007,42(1):97-103
We consider a uniformly rotating isotropic plate whose cross-section is a two-connected domain bounded from the outside by a circle of radius R and from inside by an ellipse with semiaxes a and b. The rectilinear cuts coming to the ellipse are located symmetrically on the real axis OX. On the imaginary axis OY, two point masses m are located at the distances ±id from the center of the plate. Such a plate can be considered as a plate under the action of bulk forces (forces of inertia), X, Y, and under the action of two lumped tensile forces P = mdw 2 applied at the points ±id. 相似文献
857.
858.
The use of multigrid methods in complex fluid flow problems is still under development. In this paper a full multigrid procedure has been incorporated in a finite volume solution for predicting fully developed fluid flow in a streamwise periodic geometry. Steady computations in two-dimensional body fitted co-ordinates have shown considerable savings in computation time by this multigrid method. 相似文献
859.
In this paper we examine clathrate formation in the tetraisoamylammonium propionate-water binary system. We have found formation
of four polyhydrates, two of which are metastable over the whole temperature range studied. All polyhydrate crystals were
isolated and their compositions and densities determined; for (i-C5H11)4NC2H5COO·36.5H2O, unit cell parameters were additionally found. The results are compared with data for tetra-n-butylammonium carboxylate
polyhydrates, and the structure of the title compounds is suggested. It is confirmed that the isoamyl radical stabilizes the
tetradecahedral void of the clathrate hydrate framework better than the n-butyl radical.
Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 3, pp. 67–71, May–June, 1994.
Translated by L. Smolina 相似文献
860.
L. A. Kutulya V. V. Vashchenko V. P. Kuznetsov E. E. Lakin 《Journal of Structural Chemistry》1994,35(5):688-696
X-ray diffraction analysis proved that the stereochemical configuration of interaction products of (−)-menthone with aromatic
aldehydes (α,β-unsaturated ketones or β-hydroxyketones) depends on the generation conditions of intermediate enolate carbanions.
In irreversible deprotonation of (−)-menthone with strong sterically hindered organometallic bases, products of interaction
with aldehydes preserve the 1R,4S-configuration; in equilibrium conditions, 1R,4R-diastereomers of the corresponding α,β-unsaturated
ketones are formed with high stereoselectivity.
Institute of Single Crystals, Academy of Sciences of Ukrainian Republic. Translated fromZhurnal Strukturnoi Khimii, Vol. 35, No. 5, pp. 133–142, September–October, 1994.
Translated by T. Yudanova 相似文献