Digital acoustic communication in shallow-water sea for oceanological applications

Results of experiments on slow transmission of digital information using acoustic signals in complex oceanological conditions, i.e., in the presence of multiray propagation and motion of a sound source, are given. Coding with the help of pseudorandom sequences and coherent summation of the signals transmitted along a multiplicity of different rays with different Doppler frequencies and received by different elements of an extended receiving array are performed. The used method provided an opportunity to attain errorless transmission of codes at distances larger than 5 km. A theoretical estimate is given for the probability of an erroneous decision on the value of transmitted codes.     

Acoustic Diagnosis of Internal Waves on the Black Sea Shelf According to Tomographic Experiment Data

Acoustical Physics - On the northeastern shelf of the Black Sea in 2010, a tomographic experiment was carried out on the counterpropagation of phase-shift keyed acoustic signals. During the day,...     

The advanced steam and gas technology

One of the directions of creating advanced gas and steam power units is usage of new working substances (freons) in the steam turbine stage. This paper presents the authors’ method for estimation (which is the scientific novelty) and results of calculating the efficiency and design-layout parameters of assemblies of a steamand gas power unit (SGU)with the freon technology. It is shown that the use of freons with supercritical parameters in SGU makes it possible to obtain efficiency on a level of 58% and apply more compact (compared to conventional) turbines and once-through recovery boilers, and a regenerator and condenser whose design-layout parameters are comparable with similar conventional designs.     

Acoustic tomography at shelf of the Black Sea

Using self-contained acoustic buoys developed at the Institute of Oceanology, Russian Academy of Sciences, experiments are performed to verify the possibility of acoustic tomography in a local region of a shallow-water sea. In the experiments, compound phase-manipulated signals are transmitted and the time responses of the medium are measured using three bottom-moored receiving and transmitting transducers separated by a distance of about 1 km. Identification of different groups of rays using simple models of the medium is considered. The results of reconstructing the sound and current velocities are compared with the data of independent measurements. The experiment is performed in complex weather conditions as an anticyclone passed to the experimentation region. It is shown that this acoustic tomography method is somewhat advantageous in the case of the absence of volumetric scatterers in the water bulk when the Doppler method of measuring currents fails.