Effect of the flow conditions on the metrological characteristics of a contact acoustic current meter

We discuss the results of metrological testing of a four-base acoustic current meter performed in a hydrodynamic basin, consider methodological problems encountered in the process of measurements and data processing, and present the experimental dependences of the systematic and random components of the measurement errors on the velocity and direction of the flow. Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Structure and transport of bottom waters through the chain fracture zone of the Mid-Atlantic Ridge

During the 27th cruise of the research vessel Akademik Ioffe in 2009, the measurements in the area of the main saddle of the Chain fracture zone were carried out. They included the CTD-sounding and determination of current speeds by lowered acoustic Doppler current profiler (LADCP). As a result, the structure of waters was determined and the transport of bottom waters was estimated as 0.11–0.17 Sv that is significantly less than the previous estimates. The variability of bottom potential temperature values as compared with the measurements carried out in 1991–1994 is registered. At the station situated on the main saddle, the potential temperature increased by 0.1°C and at the station located behind the saddle, it decreased by 0.034°C.     

Effects of high pressure and temperature on the properties of nanocrystals in rocks: Evidences from Raman spectroscopy

A search is conducted to detect nanocrystals in a sample of apogranitic pseudotachylite, which is a product of extremely strong crushing of granite in a seismogenic fault. Raman spectroscopy revealed nanocrystals of quartz measuring approximately 17 to 25 nm and low-temperature albite ranging from 8 to 30 nm. The crystallographic cell in the nanocrystals is deformed. The internal stresses which might have been responsible for these deformations vary from approximately −300 (compression) to +480 (tension) MPa. It is found that after having been exposed to high pressure (1 GPa) and temperature (470–500°C for 10 minutes and 550–600°C for 16 minutes), the nanocrystals of quartz reduced in size to ≈10 nm, and the nanocrystals of albite, to 13 nm. At the same time, the level of tension in the lattice spacing of quartz increased.     

Interaction of short internal waves with the ice cover in an Arctic fjord

Measurements of the short internal waves in a shallow Arctic fjord revealed that the fluctuations of the temperature and current velocity with a period of approximately 10 min and the amplitude of the internal waves around 1 m correlate with the ice cover fluctuations of the same period with an approximate amplitude of a few millimeters. These results are consistent with the theory.     

Improving the accuracy of determination of the arrival of an acoustic signal

A method is suggested for improving the accuracy of determination of the arrival of an acoustic signal emitted by a pinger of a transmitter located 2 km away from the point of signal reception. The potential accuracy of the method is analysed and the technological aspects of its realization are examined. The explanation is provided in the form of a block design, with schematic temporal diagrams being given at the most vital points. Translated by Vladimir A. Puchkin.