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41.
42.
Kostas Kleidis Apostolos Kuiroukidis Demetrios Papadopoulos Loukas Vlahos 《International Journal of Theoretical Physics》2007,46(9):2283-2298
We study the linear magnetohydrodynamic (MHD) equations, both in the Newtonian and the general-relativistic limit, as regards
a viscous magnetized fluid of finite conductivity and discuss instability criteria. In addition, we explore the excitation
of cosmological perturbations in anisotropic spacetimes, in the presence of an ambient magnetic field. Acoustic, electromagnetic
(e/m) and fast-magnetosonic modes, propagating normal to the magnetic field, can be excited, resulting in several implications
of cosmological significance. 相似文献
43.
The existence of the naphtho [9]annulenone 1 in two skeletally enantiomeric forms is demonstrated with the use of 1H? NMR. spectroscopy in conjunction with a chiral «shift» reagent. 相似文献
44.
Apostolos G. Bobos Emmanuel N. Protonotarios 《European Journal of Operational Research》1978,2(4):257-264
Deterioration of equipment is modeled as a multistate discrete time controlled Markov process. The states are classified according to the degree of deterioration. The problem of design of optimal systems for equipment maintenance and replacement is considered when the decision-maker may take, in each stage, one of many available maintenance actions, classified according to their “stochastic effectiveness”; no action and replacement are included as alternatives. It is assumed that the transition probabilities satisfy two conditions which effectively describe a trend for monotonically increasing expected deterioration and rate of deterioration. Under these assumptions it is proved in the paper that the optimal (cost minimizing) decision system in an infinite horizon is of the control limit rule type, rapidly obtained by policy improvement algorithms. A numerical example is presented for a specific practical application; detailed data are available from the authors on request. 相似文献
45.
Apostolos Hadjidimos 《Journal of Mathematical Analysis and Applications》1977,59(3):573-586
The purpose of this paper is to show the equivalence of Alternating Direction Preconditioning and Extrapolated Alternating Direction Implicit methods in the case of two-level one-parameter optimized schemes as far as convergence rates are concerned, and also to give optimum parameters for the numerical solution of the self-adjoint second-order elliptic partial differential equation and the biharmonic equation. 相似文献
46.
Roser Sabater i Serra Apostolos Kyritsis Jorge L. Escobar Ivirico Andreu Andrio Balado Jose Luis Gómez Ribelles Polykarpos Pissis Manuel Salmerón-Sánchez 《Colloid and polymer science》2010,288(5):555-565
Poly(L-lactide) networks (PmLA) hydrophilized with different amounts of 2-hydroxyethyl acrylate (HEA) were investigated by
dielectric relaxation spectroscopy, thermally stimulated depolarization currents, and differential scanning calorimetry. The
incorporation of HEA units in the PmLA network, with the aim of modulating the water sorption capacity of the system, results
in a material with a complex behavior. The system consists of phase-separated microdomains richer in one or the other comonomers
that constitute the network. Initially, the addition of smalls amount of HEA units in the network gives rise to a one-phase,
two-component system; however, when the amount of HEA in the system increases, a new phase (HEA-rich one) is formed containing
some mLA chains that modify the main relaxation mode of these domains and the local dynamics of the system. The structure
of the system has been analyzed by comparing the relaxational modes in the PmLA and PHEA homonetworks with those in the copolymer
networks. 相似文献
47.
Dimitris Gatzouras Giannopoulos Apostolos Nikolaos Markoulakis 《Discrete and Computational Geometry》2005,34(2):331-349
Let $f_{n-1}(P)$ denote the number of facets of a
polytope $P$ in ${\Bbb R}^n$. We show that there exist 0/1
polytopes $P$ with $$f_{n-1}(P)\geq\left (\frac{cn}{\log^2
n}\right )^{n/2},$$ where $c>0$ is an absolute constant. This
improves earlier work of Barany and Por on a question
of Fukuda and Ziegler. 相似文献
48.
Apostolos Hadjidimos 《Numerische Mathematik》1969,13(5):396-403
Summary Two well known high accuracy Alternating Direction Implicit difference schemes for solving Laplace's equation and the Biharmonic equation are considered. The set of iteration parameters of Douglas is used in both problems. More complete optimum values of the parameters involved are given. 相似文献
49.
Transport in Porous Media - The possibility of broaching, or the release of fluids at the seafloor due to a damaged or faulty well, is a hazard that must be assessed in the well permitting process.... 相似文献
50.
Apostolos Thoma 《manuscripta mathematica》1991,70(1):261-266
We prove that smooth monomial curves of degree greater than three are not set theoretic complete intersections on a wide class
of surfaces, called bihonogeneous surfaces. 相似文献