Application of acoustic microscopy for evaluation of numismatic material

A new non-destructive express method for assessing the authenticity of numismatic material is considered in the paper. Non-destructive methods of pulsed acoustic microscopy in the frequency range of 50-100 MHz were applied. Samples of silver coins dated 1924 and 1979 were examined. The characteristic values of the longitudinal and transverse sonic velocity of the samples were obtained. The method of hydrostatic weighing was used to measure the density of the metal. It was shown that assessment of the authenticity and the safety degree of coins can also be carried out by revealing the internal defects such as corrosion. Acoustic visualization in the reflection mode allows imaging the offset of the obverse relative to the reverse and to determine the centre of the coin deviation, which also confirms the quality of the minting.

On exact solutions of quasi-hydrodynamic system that don't satisfy the Navier-Stokes and Euler systems

Квазигидродинамическая система была предложена Шеретовым Ю.В. в 1993 году. Известные точные решения этой системы в подавляющем большинстве случаев удовлетворяют либо уравнениям Навье-Стокса, либо уравнениям Эйлера. В настоящей работе описан новый класс точных решений квазигидродинамической системы, которые не удовлетворяют ни уравнениям Навье-Стокса, ни уравнениям Эйлера. Соответствующие точные решения системы Навье-Стокса получаются из построенных решений предельным переходом при $c_s\to +\infty$, где $c_s$ - скорость звука в жидкости. The quasi-hydrodynamic system was proposed by Sheretov Yu.V. in 1993. The known exact solutions of this system in the overwhelming majority of cases satisfy either the Navier-Stokes equations or the Euler equations. This paper describes a new class of exact solutions of quasi-hydrodynamic system that satisfy neither the Navier-Stokes equations, nor the Euler equations. The corresponding exact solutions of the Navier-Stokes system are obtained from the constructed solutions by passing to the limit at $c_s\to +\infty$, where $c_s$ is the sonic velocity in the fluid.

Anisotropic Geomechanical Rock Properties Modelling for Unconventional Shale Gas Formation

Geomechanical rock properties correlations and modeling approach for conventional reservoirs are inappropriate and unsuitable for unconventional shale gas reservoirs where the shale formation is strong and has very low porosity. These correlations are critical in the development of 1D and 3D geomechanical models which are used for various field applications including drilling optimization, hydraulic fracturing design and operation, and field management. The study investigates various geomechanical rock properties and their relationships to one another using data extracted from rock mechanics testing conducted on shale core samples. For rock elastic properties correlations, dynamic elastic properties determined from compressional sonic velocity, shear sonic velocity and density are plotted against laboratory-measured static elastic properties obtained from triaxial tests. Steps were taken to further refine the properties correlations by separating the data from vertical and horizontal core samples, using data from tests conducted at in-situ confining stress condition, and focusing on data only taken from Field A and nearby fields. Similar steps were also taken to develop the correlations for rock strength properties. Correlations for the shale anisotropic elastic properties were also developed based on ratio of horizontal and vertical elastic properties. Blind tests were conducted on three wells in Field A using the new rock properties correlations which showed good matching of the predicted geomechanical properties with the new correlations and core measured test data.

Examination of rabbit liver by ultrasound

The article provides information on the study of the mechanical properties of isolated rabbit liver cells in terms of density, compressibility and ultra-sonic velocity. It was found that the values of the studied characteristics are mainly determined by the water content in the cells. The density, compressibility, and velocity of ultrasound in the cellular material are interconnected by a linear relationship.