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排序方式: 共有251条查询结果,搜索用时 15 毫秒
31.
Stefan Turek Ludmila Rivkind Jaroslav Hron Roland Glowinski 《Journal of scientific computing》2006,28(2-3):533-547
In [Turek (1996). Int. J. Numer. Meth. Fluids
22, 987–1011], we had performed numerical comparisons for different time stepping schemes for the incompressible Navier–Stokes equations. In this paper, we present the numerical analysis in the context of the Navier–Stokes equations for a modified time-stepping θ-scheme which has been recently proposed by Glowinski [Glowinski (2003). In: Ciarlet, P. G., and Lions, J. L. (eds.), Handbook of Numerical Analysis, Vol. IX, North-Holland, Amsterdam, pp. 3–1176]. Like the well-known classical Fractional-Step-θ-scheme which had been introduced by Glowinski [Glowinski (1985). In Murman, E. M. and Abarbanel, S. S. (eds.), Progress and Supercomputing in Computational Fluid Dynamics, Birkh?user, Boston MA; Bristeau et al. (1987). Comput. Phys. Rep. 6, 73–187], too, and which is still one of the most popular time stepping schemes, with or without operator splitting techniques, this new scheme consists of 3 substeps with nonequidistant substepping to build one macro time step. However, in contrast to the Fractional-Step-θ-scheme, the second substep can be formulated as an extrapolation step for previously computed data only, and the two remaining substeps look like a Backward Euler step so that no expensive operator evaluations for the right hand side vector with older solutions, as for instance in the Crank–Nicolson scheme, have to be performed. This modified scheme is implicit, strongly A-stable and second order accurate, too, which promises some advantageous behavior, particularly in implicit CFD simulations for the nonstationary Navier–Stokes equations. Representative numerical results, based on the software package FEATFLOW [Turek (2000). FEATFLOW Finite element software for the incompressible Navier–Stokes equations: User Manual, Release 1.2, University of Dortmund] are obtained for typical flow problems with benchmark character which provide a fair rating of the solution schemes, particularly in long time simulations.Dedicated to David Gottlieb on the occasion of his 60th anniversary 相似文献
32.
Ludmila A. Pavlova Lilija G. Damshkaln E. S. Vainerman 《Molecular nutrition & food research》1991,35(1):53-59
Rheological properties of concentrated dispersions of muscle Pollack proteins acetylated to different degrees as a function of temperature have been studied. The character of viscosity changes of the partially acetylated isolates is almost identical with that of unacetylated protein. However, the temperatures corresponding to viscosity maxima increase proportionally to the degree of acetylation. A total acetylation of the free lysine ?-amino groups of Pollack protein results in a significant increase in the critical concentration and/or temperature of the sol-gel transition. 相似文献
33.
Phase equilibria in the α-Ti-Al-Si region of the Ti-Si-Al system 总被引:1,自引:0,他引:1
Marina Bulanova Ludmila Tretyachenko Marina Golovkova Konstantin Meleshevich 《Journal of Phase Equilibria and Diffusion》2004,25(3):209-229
An experimental investigation of the phase relations in the titanium (Ti)-aluminum (Al)-silicon (Si) system was undertaken
by differential thermal analysis, x-ray diffraction, metallography, and microprobe analysis. The present measurements when
combined with those from an earlier investigation at this laboratory provide data for 56 alloy compositions in the Ti-Al-Si
system. The combined results allowed the construction of a solidus projection, a melting diagram including both solidus and
liquidus, partial isothermal sections at 1270 °C and 1250 °C, three isopleths with a constant percentage of one or another
component, and a reaction scheme. 相似文献
34.
In this paper we propose three variants of a linear feature extraction technique based on Adaboost for two-class classification
problems. Unlike other feature extraction techniques, we do not make any assumptions about the distribution of the data. At
each boosting step we select from a pool of linear projections the one that minimizes the weighted error. We propose three
different variants of the feature extraction algorithm, depending on the way the pool of individual projections is constructed.
Using nine real and two artificial data sets of different original dimensionality and sample size we compare the performance
of the three proposed techniques with three classical techniques for linear feature extraction: Fisher linear discriminant
analysis (FLD), Nonparametric discriminant analysis (NDA) and a recently proposed feature extraction method for heteroscedastic
data based on the Chernoff criterion. Our results show that for data sets of relatively low-original dimensionality FLD appears
to be both the most accurate and the most economical feature extraction method (giving just one-dimension in the case of two
classes). The techniques based on Adaboost fare better than the classical techniques for data sets of large original dimensionality.
相似文献
David Masip (Corresponding author)Email: |
Ludmila I. KunchevaEmail: |
35.
36.
It is shown that an algebraic interval solution of interval linear algebraic systems with matrix composed of “reverse” interval elements of the input matrix is a maximum inner estimation for the mited solution set in the sense of inclusion. 相似文献
37.
Yulia. S. Petrova Alexandr. V. Pestov Maria. K. Usoltseva Elena I Kapitanova Ludmila K. Neudachina 《分离科学与技术》2019,54(1):42-50
In this paper, we report methods for correction of selectivity of sorbents based on N-(2-sulfoethyl)chitosan towards platinum(IV) and palladium(II) in HCl solutions. The common method for correction of selectivity of the sorbents is variation of their modification degree with complexing groups. An increase in the degree of sulfoethylation of the chitosan leads to the significant increase in selectivity of sorption of palladium(II) over platinum(IV). Application of the N-(2-sulfoethyl)chitosan with the highest degree of sulfoethylation allows for selective separation palladium(II) from platinum(IV) (рН = 5.0). Palladium is quantitatively desorbed from the surface of the N-(2-sulfoethyl)chitosans by 3.5 mol/dm3 solution of HCl. 相似文献
38.
Dmitry A. Alentiev Elena S. Egorova Maxim V. Bermeshev Ludmila E. Starannikova Yuri P. Yampolskii Eugene Sh. Finkelshtein 《Polymer Engineering and Science》2019,59(12):2502-2507
Here, we report the synthesis and the study of gas‐transport properties of crosslinked highly permeable copolymers from Si‐containing norbornene derivatives. The initial high‐molecular‐weight copolymers were prepared via addition copolymerization of 3‐trimethylsilyltricyclo[4.2.1.02,5]non‐7‐ene (TCNSi1) with 3‐triethoxysilyltricyclo[4.2.1.02,5]non‐7‐ene (TCNSiOEt) in good or high yields using a Pd‐catalyst. The obtained copolymers included up to 10 mol% of TCNSiOEt units bearing reactive Si–O–C‐containing substituents. The crosslinking was readily realized by using simple sol–gel chemistry in the presence of Sn‐catalyst. The formed crosslinked copolymers were insoluble in common organic solvents. Permeability coefficients of various gases (He, H2, O2, N2, CO2, CH4, C2H6, C3H8, n‐C4H10) in these copolymers before and after crosslinking were determined and the influence of the incorporated TCNSiOEt units as well as the crosslinking on gas transport properties were established. As a result, it was found that only a small reduction of gas‐permeability was observed when TNCSiOEt units were incorporated into the main chains, and the copolymers were crosslinked. At the same time, the selectivity for C4H10/CH4 pair was increased. The suggested approach has allowed obtaining crosslinked polymers from Si‐containing monomers without a loss of the main membrane characteristics. POLYM. ENG. SCI., 59:2502–2507, 2019. © 2019 Society of Plastics Engineers 相似文献
39.
Solar Cells: Self‐Organized Superlattice and Phase Coexistence inside Thin Film Organometal Halide Perovskite (Adv. Mater. 8/2018) 下载免费PDF全文
40.
Ivan Kelnar Jaroslav Kratochvíl Ludmila Kaprálková Alexander Zhigunov Zdeněk Padovec Milan Růžička Martina Nevoralová 《应用聚合物科学杂志》2017,134(20)
Nanofillers (NF) in microfibrillar composites support melt‐drawing and may lead to improved performance. However, antagonistic effects have also been found. The deterioration of mechanical properties by drawing in the presence of NF, as found by other authors in analogous undrawn systems, has not yet been explained. Experiments indicating the importance of NF migration between the HDPE matrix and the PA6 fibrils in the course of drawing have led to a tentative conclusion of changed crystallinity in the interfacial area resulting in a layer with reduced modulus. This was confirmed by the finite element analysis considering the formation of a “soft” interface as a result of reduced content of HDPE spherulites at the fiber surfaces. The results show a marked impact of this phenomenon on modulus. This original concept presents a basis for explaining some antagonistic effects in multicomponent polymer systems and a tool for the more rational design of composite materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44712. 相似文献