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991.
In this note, we consider the scheduling problem of minimizing the sum of the weighted completion times on a single machine with one non-availability interval on the machine under the non-resumable scenario. Together with a recent 2-approximation algorithm designed by Kacem [I. Kacem, Approximation algorithm for the weighted flow-time minimization on a single machine with a fixed non-availability interval, Computers & Industrial Engineering 54 (2008) 401–410], this paper is the first successful attempt to develop a constant ratio approximation algorithm for this problem. We present two approaches to designing such an algorithm. Our best algorithm guarantees a worst-case performance ratio of 2+ε. 相似文献
992.
We develop a local flux mimetic finite difference method for second order elliptic equations with full tensor coefficients
on polyhedral meshes. To approximate the velocity (vector variable), the method uses two degrees of freedom per element edge
in two dimensions and n degrees of freedom per n-gonal mesh face in three dimensions. To approximate the pressure (scalar variable), the method uses one degree of freedom
per element. A specially chosen quadrature rule for the L
2-product of vector-functions allows for a local flux elimination and reduction of the method to a cell-centered finite difference
scheme for the pressure unknowns. Under certain assumptions, first-order convergence is proved for both variables and second-order
convergence is proved for the pressure. The assumptions are verified on simplicial meshes for a particular quadrature rule
that leads to a symmetric method. For general polyhedral meshes, non-symmetric methods are constructed based on quadrature
rules that are shown to satisfy some of the assumptions. Numerical results confirm the theory. 相似文献
993.
An efficient method is developed to construct drug-like 2,3-dihydropyrazino[1,2-a]indole-1,4-diones from 1H-indole-2-carboxylic acids, ethyl pyruvate, isocyanides, and primary amines via a one-pot, two-step procedure involving Ugi reaction and microwave-assisted cyclization. 相似文献
994.
Synthesis of fluorine containing glycolurils and oxazolines from oxides of internal perfluoroolefins
Lyudmila V. Saloutina Aleksandr Ya. Zapevalov Victor I. Saloutin Pavel A. Slepukhin Mikhail I. Kodess Oleg N. Chupakhin 《Journal of fluorine chemistry》2009,130(10):853-860
The reaction of oxides of internal perfluoroolefins 1-3 with urea gave two kinds of novel fluorine containing N-heterocyclic compounds depending on the solvent nature: 1,5-bis(perfluoroalkyl)tetraazabicyclo[3.3.0]octane-3,7-diones 4a-c and 2-amino-5-fluoro-4,5-bis(perfluoroalkyl)-4,5-dihydrooxazol-4-ols 7a-d. Use of polar dimethylsulfoxide, N,N-dimethylacetamide and acetonitrile afforded glycolurils 4a-c in moderate yields. In dioxane, unexpected cyclization occurred resulting in oxazolines 7a-d in high yields. A similar reaction of oxiranes 2, 3 with urea in aqueous dioxane gave mixtures of 4,5-dihydroxy-4,5-bis(perfluoroalkyl)imidazolidine-2-ones 9b, c, glycolurils 4b, c and oxazolines 7b-d. The molecular structure of trans-isomers of oxazoline 7b and imidazolidine 9b has been established by X-ray crystallography. 相似文献
995.
Raphaël Loubère Pierre-Henri Maire Mikhail Shashkov Jérôme Breil Stéphane Galera 《Journal of computational physics》2010,229(12):4724-4761
We present a new reconnection-based arbitrary-Lagrangian–Eulerian (ALE) method. The main elements in a standard ALE simulation are an explicit Lagrangian phase in which the solution and grid are updated, a rezoning phase in which a new grid is defined, and a remapping phase in which the Lagrangian solution is transferred (conservatively interpolated) onto the new grid. In standard ALE methods the new mesh from the rezone phase is obtained by moving grid nodes without changing connectivity of the mesh. Such rezone strategy has its limitation due to the fixed topology of the mesh. In our new method we allow connectivity of the mesh to change in rezone phase, which leads to general polygonal mesh and allows to follow Lagrangian features of the mesh much better than for standard ALE methods. Rezone strategy with reconnection is based on using Voronoi tessellation. We demonstrate performance of our new method on series of numerical examples and show it superiority in comparison with standard ALE methods without reconnection. 相似文献
996.
We suggest a new algorithm for the solution of the time domain Maxwell equations in dispersive media. After spacial discretization we obtain a large system of time-convolution equations. Then this system is projected onto a small subspace consisting of the Laplace domain solutions for a preselected set of Laplace parameters. This approach is a generalization of the rational Krylov subspace approach for the solution of non-dispersive Maxwell’s systems. We show that the projected system preserves such properties of the initial system as stability and passivity. As an example we consider the 3D quasistationary induced polarization problem with the Cole–Cole conductivity model important for geophysical oil exploration. Our numerical experiments show that the introduction of the induced polarization does not have significant effect on convergence. 相似文献
997.
Roman Kombarov Andrea Altieri Dmitry Genis Mikhail Kirpichenok Valeriy Kochubey Natalia Rakitina Zoya Titarenko 《Molecular diversity》2010,14(1):193-200
The analysis of known drugs (Comprehensive Medicinal Chemistry database (2008 version): ) and natural products (Koch et al., Proc Natl Acad Sci USA 102:17272–17277, 2008) has led to the identification of privileged
saturated and aromatic heterocyclic ring pairs that we have termed as “BioCores.” This article explains how the BioCores can
be used for the design of novel lead-like scaffolds. 相似文献
998.
Mikhail K. Volkov Eduard A. Kuraev Yury M. Bystritskiy 《Central European Journal of Physics》2010,8(4):580-586
The two-photon decay widths of scalar mesons σ(600), f 0(980) and a 0(980) as well a 0 → ju(ω)γ and f 0 → ju(ω)γ are calculated in the framework of the local Nambu-Jona-Lasinio model. The contributions of the quark loops (Hartree-Fock approximation) and the meson loops (next 1/N c -approximation where N c is the number of colors) are taken into account. The values of these contributions, as we show, are of the same order of magnitude. For the f 0 decay the K-loop contribution plays the dominant role. The results for two-gamma decays are in satisfactory agreement with modern experimental data. The predictions for a 0 → ju(ω)γ and f 0 → ju(ω)γ widths are given. 相似文献
999.
Bondarenko Darya S. Sheremet Mikhail A. Oztop Hakan F. Abu-Hamdeh Nidal 《Journal of Thermal Analysis and Calorimetry》2019,135(2):1095-1105
Journal of Thermal Analysis and Calorimetry - Convective flow and heat transfer in an alumina/water nanofluid enclosure having two centered adherent porous blocks under the effect of moving upper... 相似文献
1000.
Nadezhda S. Baleeva Anastasia V. Khavroshechkina Elvira R. Zaitseva Ivan N. Myasnyanko Marina B. Zagudaylova Mikhail S. Baranov 《Tetrahedron letters》2019,60(34):150963
The active development of fluorescence microscopy requires an increase in the variety of the dyes and their characteristics. Compounds with a large Stokes shift, i.e., a large difference between the positions of the absorption and emission maxima, have attracted the interest of researchers as a tool that can be used for multicolor labeling. One of the known approaches to increase the Stokes shift is the introduction of additional polycyclic fragments. Herein, we report novel derivatives of a conformationally locked GFP chromophore containing the naphthalene ring. The proposed modification leads not only to the enhancement of the Stokes shift up to 100 nm but also leads to the noticeable red-shift of the emission and absorption spectra in contrast with the corresponding derivatives with one benzene ring. 相似文献