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32.
Sangtae Kim Yuris O. Fuentes Seppo J. Karrila 《Journal of statistical physics》1991,62(5-6):1197-1223
Determination of many-body interactions between particles of arbitrary shape in a viscous fluid is a key problem in the simulation of concentrated suspensions. Three-dimensional flows involving such complex fluid-solid boundaries are beyond the scope of spatial methods, even on supercomputers. Boundary integral methods convert the three-dimensional PDE to a two-dimensional integral equation. Unfortunately, conventional boundary methods yield Fredholm integral equations of the first kind, and dense linear systems which are too large for accurate solution. We have pursued a different boundary integral formulation, which yields Fredholm integral equations of the second kind; these arc amenable to iterative solution. The velocity representation involves a compact operator, so a discrete spectrum results. Wielandt deflations give dramatic reductions in the spectral radius and accurate solutions are obtained after only a few iterations (typically less than 10). An analytic construction of the spectrum for sphere sphere interactions confirms these numerical results. The mathematics is similar to that encountered in the mixing ofd-atomic orbitals to form bonding/antibonding molecular orbitals in transition metals. The memory-saving version of our code can be implemented directly on a dedicated MicroVAX to solve problems involving clusters of less than a dozen particles. For a fixed number of processors, the algorithm grows essentially asN
2, whereN is the system size, so computational times are readily estimated on more powerful super-minicomputers and supercomputers using standard dot-product benchmarks. The algorithm is especially ideal for gigaflop and teraflop parallel array processors under construction in a number of computer companies; an analysis of the spectrum reveals that asynchronous iterative methods will converge, leading the way to a rigorous formulation of screening concepts for suspended particles of arbitrary shape. 相似文献
33.
Drobizhev M Stepanenko Y Dzenis Y Karotki A Rebane A Taylor PN Anderson HL 《The journal of physical chemistry. B》2005,109(15):7223-7236
Two-photon absorption spectra (2PA) of a series of conjugated dimers and the corresponding monomer were studied in the near-IR region. All of the dimers show very large peak cross section values, sigma(2) = (3-10) x 10(3) GM (1 GM = 1 x 10(-50) cm(4) s photon(-1)), which is several hundred times larger than that obtained for the corresponding monomer in the same region. We explain such dramatic cooperative enhancement by a combination of several factors, such as strong enhancement of the lowest one-photon Q-transition, better resonance conditions in the three-level system, dramatic enhancement of the excited-state singlet-singlet transition, and parallel arrangement of consecutive transitions in dimers, as compared to perpendicular arrangement in the monomer. We show that the absolute values of the 2PA cross section in these molecules are quantitatively described by a quantum-mechanical expression, derived for the three-level model. We also demonstrate the possibility of singlet oxygen generation upon one- and two-photon excitation of these dimers, which makes them particularly attractive for photodynamic therapy. 相似文献
34.
A thin metallic film deposited on a compliant polymeric substrate begins to wrinkle under compression induced in curing process
and afterwards cooling of the system. The wrinkle mode depends upon the thin film elasticity, thickness, compressive strain,
as well as mechanical properties of the compliant substrate. This paper presents a simple model to study the modulation of
the wrinkle mode of thin metallic films bonded on viscous layers in external electric field. During the procedure, linear
perturbation analysis was performed for determining the characteristic relation that governs the evolution of the plane-strain
wrinkle of the thin films under varying conditions, i.e., the maximally unstable wrinkle mode as a function of the film surface
charge, film elasticity and thickness, misfit strain, as well as thickness and viscosity of the viscous layer. It shows that,
in proper electric field, thin film may wrinkle subjected to either compression or tension. Therefore, external electric field
can be employed to modulate the wrinkle mode of thin films. The present results can be used as the theoretical basis for wrinkling
analysis and mode modulation in surface metallic coatings, drying adhesives and paints, and microelectromechanical systems
(MEMS), etc. 相似文献
35.
This paper is concerned with the electroelastic potentials and the fracture parameters of a twin-edge-cracked piezoelectric bimaterial strip with a screw dislocation. By means of conformal mapping technique and the known dislocation solution, the antiplane displacement and inplane electric potentials are obtained in closed-form. The intensity factors and the energy release rate are extracted explicitly. In some limiting cases, the present solutions cover those in the literature. 相似文献
36.
Alla Zablotskaya Izolda Segal Yuris Popelis Solveiga Grinberga Irina Shestakova Vizma Nikolajeva Daina Eze 《应用有机金属化学》2013,27(2):114-124
A series of N‐methyl‐N‐(2‐triorganylsiloxyethyl)‐1,2,3,4‐tetrahydro(iso)quinolinium iodides has been synthesized via dehydrocondensation reaction of N‐(2‐hydroxyethyl)‐1,2,3,4‐tetrahydroisoquinoline, N‐(2‐hydroxyethyl)‐1,2,3,4‐tetrahydroquinoline and 4,4‐dimethyl‐N‐(2‐hydroxyethyl)‐4‐sila‐1,2,3,4‐tetrahydroisoquinoline with trialkyl(aryl)hydrosilanes and subsequent alkylation, and characterized by 1H, 13C and 29Si NMR and mass spectroscopy. The biological activity data exhibited a marked enhancement of inhibitory activity against tumour cell lines and almost all the test bacterial/fungal strains in comparison with their 2‐hydroxyethyl precursors. Cytotoxicity in the microgram range against HT‐1080 (human fibrosarcoma) and MG‐22A (mouse hepatoma) cancer cell lines was observed for most of compounds. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
37.
The natural frequencies and decrements, velocities of sound, dynamic moduli of elasticity, and Poisson's ratios of teflon specimens have been investigated in relation to the nature of the starting powder and molding conditions. The optimal dynamic characteristics are determined and it is shown that chey can be used to optimize the molding conditions and control the quality of teflon products.Mekhanika Polimerov, Vol. 2, No. 6, pp. 917–922, 1966 相似文献
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Lyoluminescence is an interesting tool to study irradiation defects in solids and their behaviour after dissolution. A general kinetic scheme of the process valid for alkali halide crystals is presented, and some ideas about structure and properties of the interacting species, in the solid as well as in the liquid phase, are discussed. 相似文献