Model of coupled fluid flow in a reservoir and inside a horizontal well

A model and a numerical-analytic method of solving problems of single-phase adjoint fluid flow in a porous medium and in a horizontal well are proposed.Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 5, pp. 112–117, September–October, 1996.     

Low-Dentate Reagents as Titrants in Complexometry: Titration Curves in the Formation of a Mixture of Complexes

Approximate equations were derived that allow one to predict the number and heights of jumps in the potentiometric titration curves recorded for the formation of a mixture of complexes differing in coordination saturation. Criteria were proposed for the selection of promising titrants, namely, low-dentate reagents that give the only jump in the titration curve of a stepwise complexation reaction. The theoretical predictions were supported by computer experiments and by potentiometric titrations of model solutions.     

Averaged model of a cross hydrodynamic–mechanic process in a double porosity mediumModèle homogénéisé d'un processus hydrodynamique–mécanique couplé en milieu de double porosité

For the single-phase flow of a compressible liquid in a deformable double porosity medium, the closed homogenized model is obtained with a total splitting between various cross mechanic–hydrodynamic effects. The transfer between matrix and fractures is completed by the peristaltic effect and the effect of flow arising due to shearing strain. In the equation of deformations, a new stress appears being generated by the cross effects and matrix relaxation. To cite this article: M. Panfilov et al., C. R. Mecanique 334 (2006).     

Percolation characteristics of branching models of porous media

The static pattern of fluid distribution in the pore space following the penetration of fluid A into a medium initially occupied by fluid B is considered. The characteristics of the clusters formed are investigated. The cluster is simulated by a Markov type branching process, for describing which, rather than the method of cycles or the graphic technique proposed in [1, 2], the method of generating functions is used. Explicit analytic relations are obtained for the cluster parameters. Taking the dispersion of the displaced phase into account introduces nonlinearity into the governing relations, which generates another threshold effect in addition to the percolation threshold: in any medium there exists an upper threshold of possible saturation of the displaced phase different from unity. A class of media in which the formation of an infinite cluster of phase A is impossible under any conditions is identified.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 6, pp. 105–110, November–December, 1990.     

Near-Critical Gas–Liquid Flow in Porous Media: Monovariant Model, Analytical Solutions and Convective Mass Exchange Effects

We examine a class of hydrocarbon reservoirs whose thermodynamic state remains close to the critical point during the all period of reservoir exploitation. Such a situation is typical for the so-called gas–condensate systems, in which the liquid phase is formed from gas when pressure decreases. Due to proximity to critical point, the mixture contains many components which are neutral with respect to the phase state. This determines a low thermodynamic degree of freedom of the system. As the results, the mathematical flow model allows a significant reduction in the number of conservation equations, whatever the number of chemical components. In the vicinity of a well, the system may be reduced to one transport equation for saturation. This nonlinear model yields exact analytical solutions when the flow is self-similar. In more general case of flow, we develop partially linearized solutions which are shown to be sufficiently exact. The spectrum of examined cases covers the flow in a medium with a sharp heterogeneity and a sharp variation in the flow rate. A significant relative gas flow past liquid gives rise to a convective mass exchange phenomenon which appears highly different from that observed in static. In the case of a medium discontinuity, the convective mass exchange gives rise to a phenomenon of condensate saturation billow formation. A sharp variation in the flow rate leads to a hysteretic behavior of the saturation field.     

Using weighted global control for stabilizing patterned states

A general method to control a desired patterned state in reaction-diffusion processes is presented. Weighted global control is aimed to keep weighted spatially averaged properties of state variable at preset values. It is shown that weighted global control creates a stable direction in the global space of system states and affects system dynamics globally. We apply it for a specific two-component reaction-diffusion system and show that the desired pattern is attainable for a wide range of the control parameters. (c) 1999 American Institute of Physics.     

Evaluating the feasibility of using composites in ship shafting 1. Analysis of the loads and stress state of a composite shaft

Literature data is used to analyze the theoretical loads that develop in ship shafting. A study is made of the stress state of different thicknesses of shafts made of glass- and carbon-fiber-reinforced plastics loaded with an axial force, torque, and bending by a concentrated force. The results contain information needed for optimizing the design of composite ship shafting.Translated from Mekhanika Kompozitnykh Materialov, Vol. 31. No. 6, pp. 797–807. November–December, 1995.     

Dark matter constraints from an observation of dSphs and the LMC with the Baikal NT200

We have analyzed the neutrino events recoded in the deep-water neutrino experiment NT200 in Lake Baikal in five years of observations toward dark dwarf spheroidal galaxies (dSphs) in the southern hemisphere and the Large Magellanic Cloud (LMC). This analysis completes the series of works based on NT200 data in the search for a dark matter annihilation signal in astrophysical objects. We have found no significant excess in the number of observed events relative to the expected background from atmospheric neutrinos in all tested directions, in 22 dSphs and the LMC. For a sample of five selected dwarf galaxies we have performed a joint analysis of the data by the maximum likelihood method. We have obtained a correspondence of the observational data to the null hypothesis about the presence of only background events and established 90% confidence-level upper limits for the annihilation cross sections of dark matter particles with a mass from 30 GeV to 10 TeV in several annihilation channels both in the joint analysis of the selected sample of galaxies and in the analysis toward the LMC. The strongest constraints at a level of 7 × 10^–21 cm³ s^–1 have been obtained for the direction toward the LMC in the channel of annihilation into a pair of neutrinos.     

Viscoelasticity and plasticity mechanisms of human dentin

Theoretical models of viscoelastic behavior and plastic deformation mechanisms of human dentin are considered. Using the linear viscoelasticity theory in which creep and relaxation kernels have the form of fraction-exponential functions, numerical values of instantaneous and long-time Young’s moduli and other characteristics of dentin viscoelasticity under uniaxial compression are found. As dentin plastic deformation mechanisms, mutual collagen fiber sliding in the region of contact of their side surfaces, separation of these fibers from each other, and irreversible tension of some collagen fibers, are proposed. It is shown that the second mechanism activation requires a smaller stress than that for activating others. The models of plastic zones at the mode I crack tip, which correspond to these mechanisms, are studied. It is shown that the plastic zone size can increase from a few hundreds of nanometers to hundreds of micrometers with increasing applied stress.