Three-dimensional numerical simulation of a nonstationary gravitating <Emphasis Type="Italic">N</Emphasis>-body system with gas

We developed a three-dimensional numerical model to investigate nonstationary processes in gravitating N-body systems with gas. We used efficient algorithms for solving the Vlasov and Poisson equations that included the evolutionary processes under consideration, which ensures rapid convergence at high accuracy. We give examples of the numerical solution of the problem on the growth of physical instability in the model of a flat rotating disk with a gaseous component and its three-dimensional dynamics under various initial conditions including a nonzero velocity dispersion along the rotation axis.     

Methodic aspects of the measurement of pore pressure in clay soils under small strains

A technique for pore pressure measurement in triaxial tests of clay soils under small strains is considered. The essential role of the following methodic aspects of the measurements is shown, namely, the effect of temperature on the pore pressure under measurement, its difference in the central part and on the ends, and the dependence of pore pressure on strain rate.     

Cache-efficient parallel eikonal solver for multicore CPUs

Numerical solution of the eikonal equation is frequently used to compute first-arrival travel times for a given velocity model in seismic applications. Computations for large three-dimensional models become expensive requiring the use of efficient parallel solvers. We present new parallel implementations of the fast sweeping and locking sweeping methods optimized for shared memory systems such as multicore CPUs; we call them block fast sweeping method (BFSM) and block locking sweeping method (BLSM). Proposed methods are based on the domain decomposition approach with a special attention paid to high efficiency of the cache utilization and task execution synchronization. Performance tests on realistic models show high parallel efficiency of 85–95% on modern multicore CPUs and require the same number of iterations to converge as do the serial sweeping methods. We also highlight the importance of properly selecting the stopping criterion in the iterative sweeping methods aiming for a balance between computational time and accuracy of the result required by an application. In particular, we show that in seismic applications one can reach reasonable accuracy of computed travel times while dramatically reducing the number of iterations compared to the case of using the full convergence stopping criterion.     

Multispectral satellite imaging system aboard the Meteor-M No. 1 spacecraft: Three years in orbit

The multispectral satellite imaging system (MSIS) aboard the Meteor-M No. 1 spacecraft (SC) has surveyed the territory of Russia and neighboring countries in three-bands of the visible and near-IR ranges with a resolution of 60/120 m in a swath of more than 900 km for three years. The MSIS data, supple-mented by synchronous navigational information, are automatically received, pipeline processed, archived, and cataloged at ground-based receiving stations in Moscow, Novosibirsk, and Khabarovsk. These data are used to solve a wide range of land-use, environmental, and emergency monitoring problems; assess ice situations in seas, rivers, and lakes; etc. The further development of imaging instruments for operational monitoring is aimed at increasing its resolution to 20–30 m in a simultaneously expanded swath of 1600–1800 km, allowing for imaging of most of the territory of Russia with inter-orbit overlapping.     

Directional interpolation of multicomponent data

A method for interpolation of multicomponent streamer data based on using the local directionality structure is presented. The derivative components are used to estimate a vector field that locally describes the direction with the least variability. Given this vector field, the interpolation can be phrased in terms of the solution of a partial differential equation that describes how energy is transported between regions of missing data. The approach can be efficiently implemented using readily available routines for computer graphics. The method is robust to noise in the measurements and particularly towards high levels of low‐frequent noise that is present in the derivative components of the multicomponent streamer data.     

AN AUTOMATED METHOD OF HYDROLOGICAL MAPPING APPLIED TO A FOREST-WETLAND ZONE IN WEST SIBERIA

The paper describes a method for the compilation of isarithmic maps of average annual runoff for a waterlogged taiga area in West Siberia using computer algorithms. Considerable attention is devoted to such methodological issues as isarithm interpolation; determining what constitutes an adequate number of control points; and utilization of spline functions, “sieving” points, and piecewise-linear modeling. Spline-functions more precisely and reliably describe the field of annual runoff. Translated by Larry Richardson, Glendale, CA 91202 from: Geografiya i prirodnyye resursy, 1993, No. 3, pp. 20-26.     

The First Heat Flow Measurements on the Novaya Zemlya Archipelago

This paper reports the heat flow calculations that were made on the basis of the temperature measurements in the boreholes at the Pavlovskoye deposit (Novaya Zemlya), the definition of the thermal conductivity of the rocks sampled from the boreholes, and the estimation of the radiogenic thermal generation in the drilling interval. This gives the first heat flow measurements in the archipelago. The structure of the heat flow in the Novaya Zemlya archipelago is compared with other fold belts of northern Asia.

     

Properties of low‐frequency trapped mode in viscous‐fluid waveguides

We derived the velocity and attenuation of a generalized Stoneley wave being a symmetric trapped mode of a layer filled with a Newtonian fluid and embedded into either a poroelastic or a purely elastic rock. The dispersion relation corresponding to a linearized Navier–Stokes equation in a fracture coupling to either Biot or elasticity equations in the rock via proper boundary conditions was rigorously derived. A cubic equation for wavenumber was found that provides a rather precise analytical approximation of the full dispersion relation, in the frequency range of 10^?3 Hz to 10³ Hz and for layer width of less than 10 cm and fluid viscosity below 0.1 Pa· s [100 cP]. We compared our results to earlier results addressing viscous fluid in either porous rocks with a rigid matrix or in a purely elastic rock, and our formulae are found to better match the numerical solution, especially regarding attenuation. The computed attenuation was used to demonstrate detectability of fracture tip reflections at wellbore, for a range of fracture lengths and apertures, pulse frequencies, and fluid viscosity.