## A NONDESTRUCTIVE NONCONTACT METHOD OF THE SEA-BOTTOM STRUCTURE INVESTIGATION

Published in category «Experimental technique and devices»

The paper describes a nondestructive noncontact method of the sea-bottom structure investigation using hydroacoustic and laser radiation types. A practical implementation of this method is also presented. The research complex incorporates a state-of-the-art low-frequency hydroacoustic radiating system and a system of coastal laser strainmeters arranged in the sea-waters and the coastal-grounds of the special selection. The hydroacoustic radiators are put to generate a seismic signal. Seismic superficial waves are recorded by the coastal laser strainmeters. Optical parts of the strainmeters are constructed as the unequal-path Michelson interferometer where the frequency-stable helium-neon lasers serve as the emission sources. A preliminary model of the sea-bottom testing ground has been developed by application of geologic-geophysical procedures. The model-based analysis of the timing data of the recorded seismic waves was carried out. The prospectivity of the used method was proved.

## Special features of radio control link for energy efficient LED light sources

Published in category «Experimental technique and devices»

The aim of the study is to reveal the special features of radio control link model in LR-WPAN under operating conditions of interference of the reflected and the line-of-sight component and to evaluate the radio link’s range of positive light source control. The results of development and practical implementation of controlled spectrally tunable light emitting diode (LED) light sources with ISM- and ZigBee(IEEE 802.15.04)-based radio frequency transceivers are presented. A software application developed in LabVIEW simulation of a radio control link for light sources and used for evaluating the radio control link’s range of various combinations of polarization of transmitting and receiving antennas has been discussed. It was established and experimentally verified that the received energy was able to be computed using the two-ray model: a line-of-sight ray and the reflected one. This approach is simpler as compared to cellular networks in which multiple reflections from various objects result in multi-path propagation without line-of-sight component.

## Wireless networks of energy efficient dynamically controlled LED sources

Published in category «Experimental technique and devices»

The paper presents the results of development and practical implementation of wireless networks of controlled spectrally tunable light emitting diode (LED) light sources using RF transceivers operating in the unlicensed frequency bands of 868 and 2400 MHz. Such sources allow synthesizing either a white light with various color temperatures or a colored light with different tints; they are of significant interest in connection with general lighting and with some special applications. The problems of practical realization of light sources and their optimization with respect to luminous efficiency, dynamic range and the distance of wireless control have been investigated.

## Methods for reducing the patient radiation exposure during the proton eye-disease therapy

Published in category «Biophysics and medical physics»

The paper is devoted to techniques for reduction of background radiation in the room for conducting the proton eye radiotherapy. The necessity of this reduction stems from the health risk of low-dose effect on the personal and patients. We have touched the aspects of the background reduction both at the cost of secondary particles, produced in the beam-forming systems, and the dose reduction for patient’s healthy tissue (when carrying out beam-therapy) owing to the correct assessment of the biological effects of protons with energies up to 60 MeV. The obtained calculation results prove that an increase in the proton beam diameter provides the possibility of reducing the background radiation by more than a factor of three in the room and of correspondingly decreasing the body’s radiation exposure. It is necessary to take correct account of RBE to reduce the radiation exposure of contiguous organs.

## Dielectric properties and microstructure of the disintegrated nanogel films of bacterial cellulose

Published in category «Physics of molecules»

The concentration dependencies of dielectric permittivity and dielectric loss factor have been studied for the water suspensions of nanogel films of bacterial cellulose Gluconacetobacter xylinus (BC) disintegrated with the plug knives rotation speed of 15000 and 20000 rpm. The dipole moments of BC colloids have been evaluated using Buckingham statistical theory of dielectric polarization modified for binary polar systems. The number of monomer units of cellobiose in the BC colloid being equal to 113, the volume and the characteristic rotation time of the colloid particles were calculated. The difference between values of dielectric parameters for BC samples disintegrated at 15000 and 20000 rpm were within experimental error. The constant stoichiometry of BC colloids and the identity of orientation ordering of microfibrills in colloids to that of the BC nanogel films have been shown by dielectric and X-ray studies.

## Clustering algorithms application to the representative sample formation in the training of the multilayer perceptron

Published in category «Mathematics»

In this paper, we have considered the problem of effective forming the representative sample for training the neural network of the multilayer perceptron (MLP) type. An approach based on the use of clustering that allowed to increase the entropy of the training set was put forward. Various clustering algorithms were examined in order to form the representative sample. The algorithm-based clustering of factor spaces of various dimensions was carried out, and a representative sample was formed. To verify our approach we synthesized the MLP neural network and trained it. The training technique was performed with the sets formed both with and without clustering. A comparative analysis of the effectiveness of clustering algorithms was carried out in relation to the problem of representative sample formation.

## Identification procedure in the modal control of a distributed elastic system

Published in category «Mechanics»

It is necessary to provide the separation of the inherent object modes from the sensor signals and to make possible independent affecting the modes with the use of actuators when realizing the modal system of controlling an elastic object with distributed parameters. The present paper puts forward an identification procedure which allows separating the vibration modes of the object in measured and control signals in the absence of the object model simulation. The control operability of this procedure was verified by experiment through making a system of the active suppression of forced bending vibrations of a metal beam. The experiment showed the high control efficiency of the realized modal system.

## Symmetrization of the effective stress tensor for anisotropic damaged continua

Published in category «Mechanics»

A uniform formulation of the effective stress tensor symmetrization procedure has been proposed. This form contains the classical additive and multiplicative symmetrization schemes as particular cases. Different options of symmetrization of the effective stress tensor for the unidirectionally damaged material with parallel microcracks and for the bidirectionally damaged material with a system of orthogonal microcracks were compared. The differences in any forms of the effective stress tensor were second-order infinitesimals for low damage levels. The differences in predictions from considered symmetrization schemes increased with the growth of the damage level and with that of the differences between the eigenvalues of damage. An identification procedure for anisotropic damage was proposed on the basis of acoustic emission methods and then it was discussed.

## Mode III crack approaching to the wedge-shaped elastic inclusion

Published in category «Mechanics»

The problem on antiplane semi-infinite crack approaching to the elastic wedge-shaped inclusion is considered. The problem has been solved exactly using the Mellin integral transformation and the Wiener-Hopf method. The stress intensity factor of the crack tip KIII asymptotic behavior for short distances from the crack to the inclusion vicinity was studied. Depending on the composition parameters, the crack was shown to be stable (KIII → 0) or unstable (KIII → ∞). Providing that the interface has a corner point, the crack growth can be unstable (unlike the smooth interface) for some parameter values even though the crack approaches from the soft material to a relatively harder inclusion. Alternatively, the possibility of KIII → 0 exists provided the crack approaching from the hard material to a soft inclusion.

## A regularization of the Hartle-Hawking wave function

Published in category «Theoretical physics»

The paper puts forward a modification of the no-boundary Hartle-Hawking wave function in which, in the general case, the Euclidean functional integral can be described by an inhomogeneous universe. The regularization of this integral is achieved in arbitrary canonical calibration by abandoning integration over the lapse and shift functions. This makes it possible to ‘correct’ the sign of the Euclidean action corresponding to the scale factor of geometry. An additional time parameter associated with the canonical calibration condition then emerges. An additional condition for the stationary state of the wave function’s phase after returning to the Lorentzian signature, serving as the quantum equivalent of the classical principle of the least action, was used to find this time parameter. We have substantiated the interpretation of the modified wave function as the amplitude of the universe’s birth from ‘nothing’ with the additional parameter as the time of this process. A homogeneous model of the universe with a conformally invariant scalar field has been considered. In this case, two variants of the no-boundary wave function which are solutions of the Wheeler-DeWitt equation have been found.

## On the initial state of the universe in the theory of inflation

Published in category «Theoretical physics»

A toy quantum model of the inflationary universe is considered in which the role of cosmic time is played by the inflaton scalar field (its logarithm). Based on a variant of the positive energy theorem in General Relativity for the case of a closed universe, a strictly positive energy of space is introduced. The principle of minimum of the energy of space is proposed which determines a ground state as well as the excited states of the universe in quantum cosmology. According to this principle, the Beginning of the universe does exist as a state of minimal excitation of the energy of space. The initial proto-inflation quantum state of the universe is defined as a state of minimal excitation of the energy of space provided that the potential energy of the inflaton scalar field is large at the Beginning. Simultaneously, quanta of space energy excitation are introduced and the expansion of the universe can be considered as the birth of these quanta. Quantum birth of the ordinary matter becomes significant when the potential energy of the inflaton scalar field comes down to zero value.

## The topical trends in semiconductor and nanostructure physics, semiconductor opto- and nanoelectronics (on the 18th All-Russion Youth Conference)

Published in category «Actual problems of education»

The paper summarized the results of the 18th All-Russian Youth Conference on Semiconductor and Nanostructure Physics, and Semiconductor Opto- and Nanoelectronics that took place at St.Petersburg on November 28 – December 2, 2016. The reports presented in the 6 sections of the conference have been reviewed analytically. The participants whose reports were awarded certificates and money prizes by the Conference Program Committee have been mentioned. The list of reports recommended to take part in the “UMNIK” contest is presented in the nomination “Scientific results which have significant novelty and the prospect of commercialization” and shall be further funded by the Foundation for Assistance to Small Innovative Enterprises in Science and Technology.

## In memory of Alexander Ilyich Slutzker (obituary)

Published in category «Chronicle»

## In memory of Garegin Oganesovich Karapetyan (obituary)

Published in category «Chronicle»